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I have this code that uses SOCKS5 Proxy to connect to Tor and then tries to connect the Client to the remote Server on a VPS machine that runs a C# server. The problem is I can't establish the connection.
The Server is written in C#, it listens to connections on port 1604 and it's a hidden service meaning any traffic that comes trough port 1604 will be redirected to 127.0.0.1:1604 where my server listens.
Test 1
When I connected directly to test if my client get make a HTTP request to a webserver on port 80 it works, when i use the .onion address to access the webserver it works too. When I check yougetsignal using the remote machine IP it's open as you can see
Also here is the torrc FILE config
GREAT EVERYTHING WORKS SO FAR, BUT WAIT A SECOND
Test 2
When I try to connect the client to my standalone server (not a webserver) directly it works like I expected it to do, but when i try to use the HOSTNAME generated by tor.exe (the same HOSTNAME I used in Test 1) i get Connection Refused and General SOCKS server failure.
I can't find what I'm doing wrong and why I can't reach my server, please assist me and thank you for your time.
The Code
Client
Socks Code
public class ConnectionException : ApplicationException
{
public ConnectionException(string message)
: base(message)
{
}
}
/// <summary>
/// Provides sock5 functionality to clients (Connect only).
/// </summary>
public class SocksProxy
{
private SocksProxy() { }
#region ErrorMessages
private static string[] errorMsgs = {
"Operation completed successfully.",
"General SOCKS server failure.",
"Connection not allowed by ruleset.",
"Network unreachable.",
"Host unreachable.",
"Connection refused.",
"TTL expired.",
"Command not supported.",
"Address type not supported.",
"Unknown error."
};
#endregion
public static Socket ConnectToSocks5Proxy(string proxyAdress, ushort proxyPort, string destAddress, ushort destPort,
string userName, string password)
{
IPAddress destIP = null;
IPAddress proxyIP = null;
byte[] request = new byte[257];
byte[] response = new byte[257];
ushort nIndex;
try
{
proxyIP = IPAddress.Parse(proxyAdress);
}
catch (FormatException)
{ // get the IP address
proxyIP = Dns.GetHostByAddress(proxyAdress).AddressList[0];
}
// Parse destAddress (assume it in string dotted format "212.116.65.112" )
try
{
destIP = IPAddress.Parse(destAddress);
}
catch (FormatException)
{
// wrong assumption its in domain name format "www.microsoft.com"
}
IPEndPoint proxyEndPoint = new IPEndPoint(proxyIP, proxyPort);
// open a TCP connection to SOCKS server...
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
s.Connect(proxyEndPoint);
nIndex = 0;
request[nIndex++] = 0x05; // Version 5.
request[nIndex++] = 0x01; // 2 Authentication methods are in packet...
request[nIndex++] = 0x00; // NO AUTHENTICATION REQUIRED
//request[nIndex++] = 0x02; // USERNAME/PASSWORD
// Send the authentication negotiation request...
s.Send(request, nIndex, SocketFlags.None);
// Receive 2 byte response...
int nGot = s.Receive(response, 2, SocketFlags.None);
if (nGot != 2)
throw new ConnectionException("Bad response received from proxy server.");
if (response[1] == 0xFF)
{ // No authentication method was accepted close the socket.
s.Close();
throw new ConnectionException("None of the authentication method was accepted by proxy server.");
}
byte[] rawBytes;
if (/*response[1]==0x02*/false)
{//Username/Password Authentication protocol
nIndex = 0;
request[nIndex++] = 0x05; // Version 5.
// add user name
request[nIndex++] = (byte)userName.Length;
rawBytes = Encoding.Default.GetBytes(userName);
rawBytes.CopyTo(request, nIndex);
nIndex += (ushort)rawBytes.Length;
// add password
request[nIndex++] = (byte)password.Length;
rawBytes = Encoding.Default.GetBytes(password);
rawBytes.CopyTo(request, nIndex);
nIndex += (ushort)rawBytes.Length;
// Send the Username/Password request
s.Send(request, nIndex, SocketFlags.None);
// Receive 2 byte response...
nGot = s.Receive(response, 2, SocketFlags.None);
if (nGot != 2)
throw new ConnectionException("Bad response received from proxy server.");
if (response[1] != 0x00)
throw new ConnectionException("Bad Usernaem/Password.");
}
// This version only supports connect command.
// UDP and Bind are not supported.
// Send connect request now...
nIndex = 0;
request[nIndex++] = 0x05; // version 5.
request[nIndex++] = 0x01; // command = connect.
request[nIndex++] = 0x00; // Reserve = must be 0x00
if (destIP != null)
{// Destination adress in an IP.
switch (destIP.AddressFamily)
{
case AddressFamily.InterNetwork:
// Address is IPV4 format
request[nIndex++] = 0x01;
rawBytes = destIP.GetAddressBytes();
rawBytes.CopyTo(request, nIndex);
nIndex += (ushort)rawBytes.Length;
break;
case AddressFamily.InterNetworkV6:
// Address is IPV6 format
request[nIndex++] = 0x04;
rawBytes = destIP.GetAddressBytes();
rawBytes.CopyTo(request, nIndex);
nIndex += (ushort)rawBytes.Length;
break;
}
}
else
{// Dest. address is domain name.
request[nIndex++] = 0x03; // Address is full-qualified domain name.
request[nIndex++] = Convert.ToByte(destAddress.Length); // length of address.
rawBytes = Encoding.Default.GetBytes(destAddress);
rawBytes.CopyTo(request, nIndex);
nIndex += (ushort)rawBytes.Length;
}
// using big-edian byte order
byte[] portBytes = BitConverter.GetBytes(destPort);
for (int i = portBytes.Length - 1; i >= 0; i--)
request[nIndex++] = portBytes[i];
// send connect request.
s.Send(request, nIndex, SocketFlags.None);
// Point of breaking !!!!!!!!!!!!!!!!!!!!!!!!!!!!!
s.Receive(response); // Get variable length response...
if (response[1] != 0x00)
throw new ConnectionException(errorMsgs[response[1]]); // Crashes the Client !!!!!!!!!!!
// Success Connected...
return s;
}
}
Main Code
Socket s;
// s = SocksProxy.ConnectToSocks5Proxy("127.0.0.1", 9150, "xoembwt22tmxseask2qyuudbxoubiuafw54klkwuktvv6bxbhrdffqyd.onion", 1604, "U$er", "Pa$$word!"); //NOT WORKING
//s = SocksProxy.ConnectToSocks5Proxy("127.0.0.1", 9150, "xoembwt22tmxseask2qyuudbxoubiuafw54klkwuktvv6bxbhrdffqyd.onion", 80, "", ""); // WORKING
s = SocksProxy.ConnectToSocks5Proxy("127.0.0.1", 9150, "xoembwt22tmxseask2qyuudbxoubiuafw54klkwuktvv6bxbhrdffqyd.onion", 1604, "", ""); //NOT WORKING
// s = SocksProxy.ConnectToSocks5Proxy("127.0.0.1", 9150, "X.X.X.100", 1604, "", ""); //WORKING
//client is a TCPClient
client.Client = s;
Server
Server Class
public class Server : Common
{
private static int counter;
private readonly ConcurrentDictionary<int, ClientToken> clients = new ConcurrentDictionary<int, ClientToken>();
public TcpListener listener;
private Thread listenerThread;
public bool Active => listenerThread != null && listenerThread.IsAlive;
public static int NextConnectionId()
{
int id = Interlocked.Increment(ref counter);
if (id == int.MaxValue) throw new Exception("connection id limit reached: " + id);
return id;
}
private void Listen(int port)
{
try
{
listener = new TcpListener(new IPEndPoint(IPAddress.Any, port));
listener.Server.NoDelay = NoDelay;
listener.Server.SendTimeout = SendTimeout;
listener.Start();
Logger.Log("Server: listening port=" + port);
while (true)
{
TcpClient client = listener.AcceptTcpClient();
int connectionId = NextConnectionId();
ClientToken token = new ClientToken(client);
clients[connectionId] = token;
Thread sendThread = new Thread(() =>
{
try
{
SendLoop(connectionId, client, token.sendQueue, token.sendPending);
}
catch (ThreadAbortException) { }
catch (Exception exception)
{
Logger.LogError("Server send thread exception: " + exception);
}
});
sendThread.IsBackground = true;
sendThread.Start();
Thread receiveThread = new Thread(() =>
{
try
{
ReceiveLoop(connectionId, client, receiveQueue, MaxMessageSize);
clients.TryRemove(connectionId, out ClientToken _);
sendThread.Interrupt();
}
catch (Exception exception)
{
Logger.LogError("Server client thread exception: " + exception);
}
});
receiveThread.IsBackground = true;
receiveThread.Start();
}
}
catch (ThreadAbortException exception)
{
Logger.Log("Server thread aborted. That's okay. " + exception);
}
catch (SocketException exception)
{
Logger.Log("Server Thread stopped. That's okay. " + exception);
}
catch (Exception exception)
{
Logger.LogError("Server Exception: " + exception);
}
}
public bool Start(int port)
{
if (Active) return false;
receiveQueue = new ConcurrentQueue<Message>();
Logger.Log("Server: Start port=" + port);
listenerThread = new Thread(() => { Listen(port); });
listenerThread.IsBackground = true;
listenerThread.Priority = ThreadPriority.BelowNormal;
listenerThread.Start();
return true;
}
public void Stop()
{
if (!Active) return;
Logger.Log("Server: stopping...");
listener?.Stop();
listenerThread?.Interrupt();
listenerThread = null;
foreach (KeyValuePair<int, ClientToken> kvp in clients)
{
TcpClient client = kvp.Value.client;
try
{
client.GetStream().Close();
}
catch { }
client.Close();
}
clients.Clear();
}
public bool Send(int connectionId, byte[] data)
{
if (data.Length <= MaxMessageSize)
{
ClientToken token;
if (clients.TryGetValue(connectionId, out token))
{
token.sendQueue.Enqueue(data);
token.sendPending.Set();
return true;
}
Logger.Log("Server.Send: invalid connectionId: " + connectionId);
return false;
}
Logger.LogError("Client.Send: message too big: " + data.Length + ". Limit: " + MaxMessageSize);
return false;
}
public string GetClientAddress(int connectionId)
{
ClientToken token;
if (clients.TryGetValue(connectionId, out token))
return ((IPEndPoint) token.client.Client.RemoteEndPoint).Address.ToString();
return "";
}
public bool Disconnect(int connectionId)
{
ClientToken token;
if (clients.TryGetValue(connectionId, out token))
{
token.client.Close();
Logger.Log("Server.Disconnect connectionId:" + connectionId);
return true;
}
return false;
}
private class ClientToken
{
public readonly TcpClient client;
public readonly ManualResetEvent sendPending = new ManualResetEvent(false);
public readonly SafeQueue<byte[]> sendQueue = new SafeQueue<byte[]>();
public ClientToken(TcpClient client)
{
this.client = client;
}
}
}
Common
public abstract class Common
{
public static int messageQueueSizeWarning = 100000;
public int MaxMessageSize = 2147483647;
public bool NoDelay = true;
protected ConcurrentQueue<Message> receiveQueue = new ConcurrentQueue<Message>();
public int SendTimeout = 5000;
public int ReceiveQueueCount => receiveQueue.Count;
public bool GetNextMessage(out Message message)
{
return receiveQueue.TryDequeue(out message);
}
protected static bool SendMessagesBlocking(NetworkStream stream, byte[][] messages)
{
try
{
int packetSize = 0;
for (int i = 0; i < messages.Length; ++i)
packetSize += sizeof(int) + messages[i].Length;
byte[] payload = new byte[packetSize];
int position = 0;
for (int i = 0; i < messages.Length; ++i)
{
byte[] header = Utils.IntToBytesBigEndian(messages[i].Length);
Array.Copy(header, 0, payload, position, header.Length);
Array.Copy(messages[i], 0, payload, position + header.Length, messages[i].Length);
position += header.Length + messages[i].Length;
}
stream.Write(payload, 0, payload.Length);
return true;
}
catch (Exception exception)
{
Logger.Log("Send: stream.Write exception: " + exception);
return false;
}
}
protected static bool ReadMessageBlocking(NetworkStream stream, int MaxMessageSize, out byte[] content)
{
content = null;
byte[] header = new byte[4];
if (!stream.ReadExactly(header, 4))
return false;
int size = Utils.BytesToIntBigEndian(header);
if (size <= MaxMessageSize)
{
content = new byte[size];
return stream.ReadExactly(content, size);
}
Logger.LogWarning("ReadMessageBlocking: possible allocation attack with a header of: " + size + " bytes.");
return false;
}
protected static void ReceiveLoop(int connectionId, TcpClient client, ConcurrentQueue<Message> receiveQueue,
int MaxMessageSize)
{
NetworkStream stream = client.GetStream();
DateTime messageQueueLastWarning = DateTime.Now;
try
{
receiveQueue.Enqueue(new Message(connectionId, EventType.Connected, null));
while (true)
{
byte[] content;
if (!ReadMessageBlocking(stream, MaxMessageSize, out content))
break;
receiveQueue.Enqueue(new Message(connectionId, EventType.Data, content));
if (receiveQueue.Count > messageQueueSizeWarning)
{
TimeSpan elapsed = DateTime.Now - messageQueueLastWarning;
if (elapsed.TotalSeconds > 10)
{
Logger.LogWarning("ReceiveLoop: messageQueue is getting big(" + receiveQueue.Count +
"), try calling GetNextMessage more often. You can call it more than once per frame!");
messageQueueLastWarning = DateTime.Now;
}
}
}
}
catch (Exception exception)
{
Logger.Log("ReceiveLoop: finished receive function for connectionId=" + connectionId + " reason: " +
exception);
}
stream.Close();
client.Close();
receiveQueue.Enqueue(new Message(connectionId, EventType.Disconnected, null));
}
protected static void SendLoop(int connectionId, TcpClient client, SafeQueue<byte[]> sendQueue,
ManualResetEvent sendPending)
{
NetworkStream stream = client.GetStream();
try
{
while (client.Connected)
{
sendPending.Reset();
byte[][] messages;
if (sendQueue.TryDequeueAll(out messages))
if (!SendMessagesBlocking(stream, messages))
return;
sendPending.WaitOne();
}
}
catch (ThreadAbortException) { }
catch (ThreadInterruptedException) { }
catch (Exception exception)
{
Logger.Log("SendLoop Exception: connectionId=" + connectionId + " reason: " + exception);
}
}
}
I'm trying to implement wrapper class which will simply connect to TCP server and wait for data. Once data submitted from server - I will receive this data and pass it onto subscribers of my class.
All this works. Now I want to add external functionality to "reset" this class on a timer (force reconnect every so often) to keep connection alive. My idea is that Init method can be called as many times as needed to get socket reset. However, I do get various exceptions with this.
Class code:
namespace Ditat.GateControl.Service.InputListener
{
using System;
using System.ComponentModel;
using System.Net;
using System.Net.Sockets;
using System.Text;
public class BaseTCPSocketListener : IInputListener
{
#region Events/Properties
public event EventHandler<Exception> OnError;
public event EventHandler<string> OnDataReceived;
private string host;
private int port;
private int delayToClearBufferSeconds = 5;
private TcpClient client;
private readonly byte[] buffer = new byte[1024];
/// <summary>
/// Will accumulate data as it's received
/// </summary>
private string DataBuffer { get; set; }
/// <summary>
/// Store time of last data receipt. Need this in order to purge data after delay
/// </summary>
private DateTime LastDataReceivedOn { get; set; }
#endregion
public BaseTCPSocketListener()
{
// Preset all entries
this.LastDataReceivedOn = DateTime.UtcNow;
this.DataBuffer = string.Empty;
}
public void Init(string config)
{
// Parse info
var bits = config.Split(new[] { '|' }, StringSplitOptions.RemoveEmptyEntries);
this.host = bits[0];
var hostBytes = this.host.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries);
var hostIp = new IPAddress(new[] { byte.Parse(hostBytes[0]), byte.Parse(hostBytes[1]), byte.Parse(hostBytes[2]), byte.Parse(hostBytes[3]) });
this.port = int.Parse(bits[1]);
this.delayToClearBufferSeconds = int.Parse(bits[2]);
// Close open client
if (this.client?.Client != null)
{
this.client.Client.Disconnect(true);
this.client = null;
}
// Connect to client
this.client = new TcpClient();
if (!this.client.ConnectAsync(hostIp, this.port).Wait(2500))
throw new Exception($"Failed to connect to {this.host}:{this.port} in allotted time");
this.EstablishReceiver();
}
protected void DataReceived(IAsyncResult result)
{
// End the data receiving that the socket has done and get the number of bytes read.
var bytesCount = 0;
try
{
bytesCount = this.client.Client.EndReceive(result);
}
catch (Exception ex)
{
this.RaiseOnErrorToClient(new Exception(nameof(this.DataReceived)));
this.RaiseOnErrorToClient(ex);
}
// No data received, establish receiver and return
if (bytesCount == 0)
{
this.EstablishReceiver();
return;
}
// Convert the data we have to a string.
this.DataBuffer += Encoding.UTF8.GetString(this.buffer, 0, bytesCount);
// Record last time data received
this.LastDataReceivedOn = DateTime.UtcNow;
this.RaiseOnDataReceivedToClient(this.DataBuffer);
this.DataBuffer = string.Empty;
this.EstablishReceiver();
}
private void EstablishReceiver()
{
try
{
// Set up again to get the next chunk of data.
this.client.Client.BeginReceive(this.buffer, 0, this.buffer.Length, SocketFlags.None, this.DataReceived, this.buffer);
}
catch (Exception ex)
{
this.RaiseOnErrorToClient(new Exception(nameof(this.EstablishReceiver)));
this.RaiseOnErrorToClient(ex);
}
}
private void RaiseOnErrorToClient(Exception ex)
{
if (this.OnError == null) return;
foreach (Delegate d in this.OnError.GetInvocationList())
{
var syncer = d.Target as ISynchronizeInvoke;
if (syncer == null)
{
d.DynamicInvoke(this, ex);
}
else
{
syncer.BeginInvoke(d, new object[] { this, ex });
}
}
}
private void RaiseOnDataReceivedToClient(string data)
{
if (this.OnDataReceived == null) return;
foreach (Delegate d in this.OnDataReceived.GetInvocationList())
{
var syncer = d.Target as ISynchronizeInvoke;
if (syncer == null)
{
d.DynamicInvoke(this, data);
}
else
{
syncer.BeginInvoke(d, new object[] { this, data });
}
}
}
}
}
Client code (under button click on form)
private void ListenBaseButton_Click(object sender, EventArgs e)
{
if (this.bsl == null)
{
this.bsl = new BaseTCPSocketListener();
this.bsl.OnDataReceived += delegate (object o, string s)
{
this.DataTextBox.Text += $"Base: {DateTime.Now} - {s}" + Environment.NewLine;
};
this.bsl.OnError += delegate (object o, Exception x)
{
this.DataTextBox.Text += $"Base TCP receiver error: {DateTime.Now} - {x.Message}" + Environment.NewLine;
};
}
try
{
this.bsl.Init("192.168.33.70|10001|10");
this.DataTextBox.Text += "BEGIN RECEIVING BSL data --------------------------" + Environment.NewLine;
}
catch (Exception exception)
{
this.DataTextBox.Text += $"ERROR CONNECTING TO BSL ------------{exception.Message}" + Environment.NewLine;
}
}
Exceptions I get. First exception when button clicked 2nd time in from handler in DataReceived
The IAsyncResult object was not returned from the corresponding
asynchronous method on this class.
On following clicks I get exception from handler in EstablishReceiver
A request to send or receive data was disallowed because the socket is
not connected and (when sending on a datagram socket using a sendto
call) no address was supplied
How do I properly ensure socket closed and re-opened?
The IAsyncResult object was not returned from the corresponding
asynchronous method on this class.
This is a well known problem that happens when data callback (DataReceived()) is called for previous socket. In this case you will call Socket.EndReceive() with incorrect instance of IAsyncResult which throws above exception.
Asynchronous Client Socket Example contains possible workaround for this problem: store socket on which BeginReceive() was called in state object which is then passed to DataReceived callback:
StateObject class
public class StateObject
{
public Socket Socket { get; set; }
public byte[] Buffer { get; } = new byte[1024];
public StateObject(Socket socket)
{
Socket = socket;
}
}
EstablishReceiver() method:
private void EstablishReceiver()
{
try
{
var state = new StateObject(client.Client);
// Set up again to get the next chunk of data.
this.client.Client.BeginReceive(state.Buffer, 0, state.Buffer.Length, SocketFlags.None, this.DataReceived, state);
}
catch (Exception ex)
{
this.RaiseOnErrorToClient(new Exception(nameof(this.EstablishReceiver)));
this.RaiseOnErrorToClient(ex);
}
}
DataReceived() method:
protected void DataReceived(IAsyncResult result)
{
var state = (StateObject) result.AsyncState;
// End the data receiving that the socket has done and get the number of bytes read.
var bytesCount = 0;
try
{
SocketError errorCode;
bytesCount = state.Socket.EndReceive(result, out errorCode);
if (errorCode != SocketError.Success)
{
bytesCount = 0;
}
}
catch (Exception ex)
{
this.RaiseOnErrorToClient(new Exception(nameof(this.DataReceived)));
this.RaiseOnErrorToClient(ex);
}
if (bytesCount > 0)
{
// Convert the data we have to a string.
this.DataBuffer += Encoding.UTF8.GetString(state.Buffer, 0, bytesCount);
// Record last time data received
this.LastDataReceivedOn = DateTime.UtcNow;
this.RaiseOnDataReceivedToClient(this.DataBuffer);
this.DataBuffer = string.Empty;
this.EstablishReceiver();
}
}
A request to send or receive data was disallowed because the socket is
not connected and (when sending on a datagram socket using a sendto
call) no address was supplied
Above DataReceived() method also contains the fix for the second exception. Exception is caused by calling BeginReceive() (from EstablishReceiver()) on disconnected socket. You should not call BeginReceive() on a socket if previous read brought 0 bytes.
First of all, you're closing the socket being held by the TcpClient, but not disposing the client itself. Try the following:
// Close open client
this.client?.Close(); // Disposes and releases resources
this.client = null;
The issue is that DataReceived will be called when you close the client. You simply need to identify to the method that it should not do anything because you have deliberately ended the process. You could just add a bool:
private bool ignoreCallback;
public void Init(string config)
{
// Parse info
var bits = config.Split(new[] { '|' }, StringSplitOptions.RemoveEmptyEntries);
this.host = bits[0];
var hostBytes = this.host.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries);
var hostIp = new IPAddress(new[] { byte.Parse(hostBytes[0]), byte.Parse(hostBytes[1]), byte.Parse(hostBytes[2]), byte.Parse(hostBytes[3]) });
this.port = int.Parse(bits[1]);
this.delayToClearBufferSeconds = int.Parse(bits[2]);
// Close open client
if (this.client?.Client != null)
{
ignoreCallback = true;
this.client.Client.Disconnect(true);
this.client = null;
}
// Connect to client
this.client = new TcpClient();
if (!this.client.ConnectAsync(hostIp, this.port).Wait(2500))
throw new Exception($"Failed to connect to {this.host}:{this.port} in allotted time");
this.EstablishReceiver();
}
protected void DataReceived(IAsyncResult result)
{
if (ignoreCallback)
{
ignoreCallback = false;
return;
}
...
I'm trying to build a command line chat room where the server is handling the connections and repeating input from one client back to all the other clients.
Currently the server is able to take in input from multiple clients, but can only send information back to those clients individually. I think my problem is that each connection is being handled on an individual thread. How would I allow for the threads to communicate with each other or be able to send data to each thread?
Server code:
namespace ConsoleApplication
{
class TcpHelper
{
private static object _lock = new object();
private static List<Task> _connections = new List<Task>();
private static TcpListener listener { get; set; }
private static bool accept { get; set; } = false;
private static Task StartListener()
{
return Task.Run(async () =>
{
IPAddress address = IPAddress.Parse("127.0.0.1");
int port = 5678;
listener = new TcpListener(address, port);
listener.Start();
Console.WriteLine($"Server started. Listening to TCP clients at 127.0.0.1:{port}");
while (true)
{
var tcpClient = await listener.AcceptTcpClientAsync();
Console.WriteLine("Client has connected");
var task = StartHandleConnectionAsync(tcpClient);
if (task.IsFaulted)
task.Wait();
}
});
}
// Register and handle the connection
private static async Task StartHandleConnectionAsync(TcpClient tcpClient)
{
// start the new connection task
var connectionTask = HandleConnectionAsync(tcpClient);
// add it to the list of pending task
lock (_lock)
_connections.Add(connectionTask);
// catch all errors of HandleConnectionAsync
try
{
await connectionTask;
}
catch (Exception ex)
{
// log the error
Console.WriteLine(ex.ToString());
}
finally
{
// remove pending task
lock (_lock)
_connections.Remove(connectionTask);
}
}
private static async Task HandleConnectionAsync(TcpClient client)
{
await Task.Yield();
{
using (var networkStream = client.GetStream())
{
if (client != null)
{
Console.WriteLine("Client connected. Waiting for data.");
StreamReader streamreader = new StreamReader(networkStream);
StreamWriter streamwriter = new StreamWriter(networkStream);
string clientmessage = "";
string servermessage = "";
while (clientmessage != null && clientmessage != "quit")
{
clientmessage = await streamreader.ReadLineAsync();
Console.WriteLine(clientmessage);
servermessage = clientmessage;
streamwriter.WriteLine(servermessage);
streamwriter.Flush();
}
Console.WriteLine("Closing connection.");
networkStream.Dispose();
}
}
}
}
public static void Main(string[] args)
{
// Start the server
Console.WriteLine("Hit Ctrl-C to close the chat server");
TcpHelper.StartListener().Wait();
}
}
}
Client Code:
namespace Client2
{
public class Program
{
private static void clientConnect()
{
TcpClient socketForServer = new TcpClient();
bool status = true;
string userName;
Console.Write("Input Username: ");
userName = Console.ReadLine();
try
{
IPAddress address = IPAddress.Parse("127.0.0.1");
socketForServer.ConnectAsync(address, 5678);
Console.WriteLine("Connected to Server");
}
catch
{
Console.WriteLine("Failed to Connect to server{0}:999", "localhost");
return;
}
NetworkStream networkStream = socketForServer.GetStream();
StreamReader streamreader = new StreamReader(networkStream);
StreamWriter streamwriter = new StreamWriter(networkStream);
try
{
string clientmessage = "";
string servermessage = "";
while (status)
{
Console.Write(userName + ": ");
clientmessage = Console.ReadLine();
if ((clientmessage == "quit") || (clientmessage == "QUIT"))
{
status = false;
streamwriter.WriteLine("quit");
streamwriter.WriteLine(userName + " has left the conversation");
streamwriter.Flush();
}
if ((clientmessage != "quit") && (clientmessage != "quit"))
{
streamwriter.WriteLine(userName + ": " + clientmessage);
streamwriter.Flush();
servermessage = streamreader.ReadLine();
Console.WriteLine("Server:" + servermessage);
}
}
}
catch
{
Console.WriteLine("Exception reading from the server");
}
streamreader.Dispose();
networkStream.Dispose();
streamwriter.Dispose();
}
public static void Main(string[] args)
{
clientConnect();
}
}
}
The main thing wrong in your code is that you make no attempt to send data received from one client to the other connected clients. You have the _connections list in your server, but the only thing stored in the list are the Task objects for the connections, and you don't even do anything with those.
Instead, you should maintain a list of the connections themselves, so that when you received a message from one client, you can then retransmit that message to the other clients.
At a minimum, this should be a List<TcpClient>, but because you are using StreamReader and StreamWriter, you'll want to initialize and store those objects in the list as well. In addition, you should include a client identifier. One obvious choice for this would be the name of the client (i.e. what the user enters as their name), but your example doesn't provide any mechanism in the chat protocol to transmit that identification as part of the connection initialization, so in my example (below) I just use a simple integer value.
There are some other irregularities in the code you posted, such as:
Starting a task in a brand new thread, just to execute a few statements that get you to the point of initiating an asynchronous operation. In my example, I simply omit the Task.Run() part of the code, as it's not needed.
Checking the connection-specific task when it's returned for IsFaulted. Since it's unlikely any I/O will actually have occurred by the time this Task object is returned, this logic has very little use. The call to Wait() will throw an exception, which will propagate to the main thread's Wait() call, terminating the server. But you don't terminate the server in the event of any other error, so it's not clear why you'd want to do that here.
There's a spurious call to Task.Yield(). I have no idea what you're trying to accomplish there, but whatever it is, that statement isn't useful. I simply removed it.
In your client code, you only attempt to receive data from the server when you've sent data. This is very wrong; you want clients to be responsive and receive data as soon as it's sent to them. In my version, I included a simple little anonymous method that is called immediately to start a separate message-receiving loop that will execute asynchronously and concurrently with the main user input loop.
Also in the client code, you were sending the "…has left…" message after the "quit" message that would cause the server to close the connection. This means that the server would never actually receive the "…has left…" message. I reversed the order of the messages so that "quit" is always the last thing the client ever sends.
My version looks like this:
Server:
class TcpHelper
{
class ClientData : IDisposable
{
private static int _nextId;
public int ID { get; private set; }
public TcpClient Client { get; private set; }
public TextReader Reader { get; private set; }
public TextWriter Writer { get; private set; }
public ClientData(TcpClient client)
{
ID = _nextId++;
Client = client;
NetworkStream stream = client.GetStream();
Reader = new StreamReader(stream);
Writer = new StreamWriter(stream);
}
public void Dispose()
{
Writer.Close();
Reader.Close();
Client.Close();
}
}
private static readonly object _lock = new object();
private static readonly List<ClientData> _connections = new List<ClientData>();
private static TcpListener listener { get; set; }
private static bool accept { get; set; }
public static async Task StartListener()
{
IPAddress address = IPAddress.Any;
int port = 5678;
listener = new TcpListener(address, port);
listener.Start();
Console.WriteLine("Server started. Listening to TCP clients on port {0}", port);
while (true)
{
var tcpClient = await listener.AcceptTcpClientAsync();
Console.WriteLine("Client has connected");
var task = StartHandleConnectionAsync(tcpClient);
if (task.IsFaulted)
task.Wait();
}
}
// Register and handle the connection
private static async Task StartHandleConnectionAsync(TcpClient tcpClient)
{
ClientData clientData = new ClientData(tcpClient);
lock (_lock) _connections.Add(clientData);
// catch all errors of HandleConnectionAsync
try
{
await HandleConnectionAsync(clientData);
}
catch (Exception ex)
{
// log the error
Console.WriteLine(ex.ToString());
}
finally
{
lock (_lock) _connections.Remove(clientData);
clientData.Dispose();
}
}
private static async Task HandleConnectionAsync(ClientData clientData)
{
Console.WriteLine("Client connected. Waiting for data.");
string clientmessage;
while ((clientmessage = await clientData.Reader.ReadLineAsync()) != null && clientmessage != "quit")
{
string message = "From " + clientData.ID + ": " + clientmessage;
Console.WriteLine(message);
lock (_lock)
{
// Locking the entire operation ensures that a) none of the client objects
// are disposed before we can write to them, and b) all of the chat messages
// are received in the same order by all clients.
foreach (ClientData recipient in _connections.Where(r => r.ID != clientData.ID))
{
recipient.Writer.WriteLine(message);
recipient.Writer.Flush();
}
}
}
Console.WriteLine("Closing connection.");
}
}
Client:
class Program
{
private const int _kport = 5678;
private static async Task clientConnect()
{
IPAddress address = IPAddress.Loopback;
TcpClient socketForServer = new TcpClient();
string userName;
Console.Write("Input Username: ");
userName = Console.ReadLine();
try
{
await socketForServer.ConnectAsync(address, _kport);
Console.WriteLine("Connected to Server");
}
catch (Exception e)
{
Console.WriteLine("Failed to Connect to server {0}:{1}", address, _kport);
return;
}
using (NetworkStream networkStream = socketForServer.GetStream())
{
var readTask = ((Func<Task>)(async () =>
{
using (StreamReader reader = new StreamReader(networkStream))
{
string receivedText;
while ((receivedText = await reader.ReadLineAsync()) != null)
{
Console.WriteLine("Server:" + receivedText);
}
}
}))();
using (StreamWriter streamwriter = new StreamWriter(networkStream))
{
try
{
while (true)
{
Console.Write(userName + ": ");
string clientmessage = Console.ReadLine();
if ((clientmessage == "quit") || (clientmessage == "QUIT"))
{
streamwriter.WriteLine(userName + " has left the conversation");
streamwriter.WriteLine("quit");
streamwriter.Flush();
break;
}
else
{
streamwriter.WriteLine(userName + ": " + clientmessage);
streamwriter.Flush();
}
}
await readTask;
}
catch (Exception e)
{
Console.WriteLine("Exception writing to server: " + e);
throw;
}
}
}
}
public static void Main(string[] args)
{
clientConnect().Wait();
}
}
There is still a lot you'll need to work on. You'll probably want to implement proper initialization of chat user names on the server side. At the very least, for real-world code you'd want to do more error checking, and make sure the client ID is generated reliably (if you only want positive ID values, you can't have more than 2^31-1 connections before it rolls back over to 0).
I also made some other minor changes that weren't strictly necessary, such as using the IPAddress.Any and IPAddress.Loopback values instead of parsing strings, and just generally simplifying and cleaning up the code here and there. Also, I'm not using a C# 6 compiler at the moment, so I changed the code where you were using C# 6 features so that it would compile using C# 5 instead.
To do a full-blown chat server, you still have your work cut out for you. But I hope that the above gets you back on the right track.
I am making a chat service for a game,
I am using a TCP listener an client for the account information, some sort of login service. I'm wondering if i can keep the socked the client connected to the server with, to check if he is still online, and keep sending him messages if he has new messages.
I already tried making a list of sockets for the login queue, but it disconnected the previous socket to to server as soon as i accepted a new socket.
byte[] usernameByte = new byte[100];
int usernameRecieved = s.Receive(usernameByte);
//guiController.setText(System.DateTime.Now + " Recieved Login...");
byte[] passByte = new byte[100];
int passRecieved = s.Receive(passByte);
//guiController.setText(System.DateTime.Now + " Recieved Password...");
string username = "";
string password = "";
for (int i = 0; i < usernameRecieved; i++)
username += (Convert.ToChar(usernameByte[i]));
for (int i = 0; i < passRecieved; i++)
password += (Convert.ToChar(passByte[i]));
if (DomainController.getInstance().checkAccount(username, password))
{
ASCIIEncoding asen = new ASCIIEncoding();
s.Send(asen.GetBytes("true"));
s.Send(asen.GetBytes("U are succesfully logged in, press enter to continue"));
guiController.setText(serverName,System.DateTime.Now+"");
guiController.setText(serverName, "Sent Acknowledgement - Logged in");
}
else
{
ASCIIEncoding asen = new ASCIIEncoding();
s.Send(asen.GetBytes("false"));
s.Send(asen.GetBytes("U are NOT logged in, press enter to continue"));
guiController.setText(serverName, System.DateTime.Now + "");
guiController.setText(serverName, "\nSent Acknowledgement - Not logged in");
}
This is the code i currently use to check the account information the user send me. Right after i send this the user dropd the connection and i move on to the next one.
I have tried making 1 list of seperate sockets and processing them one by one, but that failed because the previous socket's connection dropped, even tho it were 2 different machines that tried to connect.
Does anyone have a sollution / a way to save sockets, that I can use to make the program keep all the connections alive? so i can send a message from user 1 to user 2, and just use the socket they connected with? or do i need to add an id every time they make a connection?
EDIT
The client Code: (this is just a test client)
while (true)
{
TcpClient tcpclnt = new TcpClient();
Console.WriteLine("Connecting.....");
tcpclnt.Connect("xx.xxx.xxx.xx", 26862);
// use the ipaddress as in the server program
while(!(checkResponse(tcpclnt.GetStream())))
{
Thread.Sleep(1000);
}
Console.WriteLine("Connected");
Console.Write("Enter the string to be transmitted : ");
String str = Console.ReadLine();
if (str == "")
{
str = " ";
}
Stream stm = tcpclnt.GetStream();
ASCIIEncoding asen = new ASCIIEncoding();
byte[] ba = asen.GetBytes(str);
Console.WriteLine("Transmitting.....");
stm.Write(ba, 0, ba.Length);
Console.Write("Enter the string to be transmitted : ");
String str2 = Console.ReadLine();
if (str2 == "")
{
str2 = " ";
}
Stream stm2 = tcpclnt.GetStream();
ASCIIEncoding asen2 = new ASCIIEncoding();
byte[] ba2 = asen2.GetBytes(str2);
Console.WriteLine("Transmitting.....");
stm.Write(ba2, 0, ba2.Length);
if (str == "false")
{
blijvenWerken = false;
}
byte[] bb = new byte[100];
int k = stm.Read(bb, 0, 100);
for (int i = 0; i < k; i++)
Console.Write(Convert.ToChar(bb[i]));
byte[] bb2 = new byte[100];
int k2 = stm.Read(bb2, 0, 100);
Console.Write("\n");
for (int i = 0; i < k2; i++)
Console.Write(Convert.ToChar(bb2[i]));
Console.WriteLine("\n");
tcpclnt.Close();
Thread.Sleep(1000);
}
Server getting the sockets:
This bit of code is on the loginserver, its because i can only accept 1 socket every time to keep the connection alive, that i put queueCount on a maximum of 1.
I want to be able to make a list of Sockets that i accepted to add to a User account.
while (loginServerOn)
{
if (queueCount < 1)
{
if (loginServer.getLoginListener().Pending())
{
loginQueue.Add(loginServer.getSocket());
ASCIIEncoding asen = new ASCIIEncoding();
Socket s = loginQueue.First();
try
{
s.Send(asen.GetBytes("true"));
queueCount++;
}
catch
{
loginQueue.Remove(s);
}
}
}
}
The function that returns the accepted socket.
public Socket getSocket()
{
return myList.AcceptSocket();
}
EDIT: Essence of the question
I want to add the socked or client recieved to my Account object, so every connection has an Account its linked to, when i want to send a message to a certain account, it should send a message to the socked or client bound to that account, can you help/show me how i can achieve this?
This is still c# and sockets but my approach is different to yours.
I went with the concept of a "connectedCleint" which is similar in purpose to what you've called an account.
I have a class called ServerTerminal which is responsible for accepting and top level management of socket connections. In this i've got:
public Dictionary<long, ConnectedClient> DictConnectedClients =
new Dictionary<long, ConnectedClient>();
So this is my list of connected clients indexed by the sockethandle.
To accept connections i've got a routine:
public void StartListen(int port)
{
socketClosed = false;
IPEndPoint ipLocal = new IPEndPoint(IPAddress.Any, port);
listenSocket = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
//bind to local IP Address...
//if ip address is allready being used write to log
try
{
listenSocket.Bind(ipLocal);
}
catch (Exception excpt)
{
// Deal with this.. write your own log code here ?
socketClosed = true;
return;
}
//start listening...
listenSocket.Listen(100); // Max 100 connections for my app
// create the call back for any client connections...
listenSocket.BeginAccept(new AsyncCallback(OnClientConnection), null);
}
So when a client connects it then fires off:
private void OnClientConnection(IAsyncResult asyn)
{
if (socketClosed)
{
return;
}
try
{
Socket clientSocket = listenSocket.EndAccept(asyn);
ConnectedClient connectedClient = new ConnectedClient(clientSocket, this, _ServerTerminalReceiveMode);
//connectedClient.MessageReceived += OnMessageReceived;
connectedClient.Disconnected += OnDisconnection;
connectedClient.dbMessageReceived += OndbMessageReceived;
connectedClient.ccSocketFaulted += ccSocketFaulted;
connectedClient.StartListening();
long key = clientSocket.Handle.ToInt64();
if (DictConnectedClients.ContainsKey(connectedClient.SocketHandleInt64))
{
// Already here - use your own error reporting..
}
lock (DictConnectedClients)
{
DictConnectedClients[key] = connectedClient;
}
// create the call back for any client connections...
listenSocket.BeginAccept(new AsyncCallback(OnClientConnection), null);
}
catch (ObjectDisposedException excpt)
{
// Your own code here..
}
catch (Exception excpt)
{
// Your own code here...
}
}
The crucial part of this for you is:
// create the call back for any client connections...
listenSocket.BeginAccept(new AsyncCallback(OnClientConnection), null);
This sets up the serverterminal to receive new connections.
Edit:
Cut down version of my connectedclient:
public class ConnectedClient
{
private Socket mySocket;
private SocketIO mySocketIO;
private long _mySocketHandleInt64 = 0;
// These events are pass through; ConnectedClient offers them but really
// they are from SocketIO
public event TCPTerminal_ConnectDel Connected
{
add
{
mySocketIO.Connected += value;
}
remove
{
mySocketIO.Connected -= value;
}
}
public event TCPTerminal_DisconnectDel Disconnected
{
add
{
mySocketIO.Disconnected += value;
}
remove
{
mySocketIO.Disconnected -= value;
}
}
// Own Events
public event TCPTerminal_TxMessagePublished TxMessageReceived;
public delegate void SocketFaulted(ConnectedClient cc);
public event SocketFaulted ccSocketFaulted;
private void OnTxMessageReceived(Socket socket, TxMessage myTxMessage)
{
// process your message
}
private void OnMessageSent(int MessageNumber, int MessageType)
{
// successful send, do what you want..
}
public ConnectedClient(Socket clientSocket, ServerTerminal ParentST)
{
Init(clientSocket, ParentST, ReceiveMode.Handler);
}
public ConnectedClient(Socket clientSocket, ServerTerminal ParentST, ReceiveMode RecMode)
{
Init(clientSocket, ParentST, RecMode);
}
private void Init(Socket clientSocket, ServerTerminal ParentST, ReceiveMode RecMode)
{
ParentServerTerminal = ParentST;
_myReceiveMode = RecMode;
_FirstConnected = DateTime.Now;
mySocket = clientSocket;
_mySocketHandleInt64 = mySocket.Handle.ToInt64();
mySocketIO = new SocketIO(clientSocket, RecMode);
// Register for events
mySocketIO.TxMessageReceived += OnTxMessageReceived;
mySocketIO.MessageSent += OnMessageSent;
mySocketIO.dbMessageReceived += OndbMessageReceived;
}
public void StartListening()
{
mySocketIO.StartReceiving();
}
public void Close()
{
if (mySocketIO != null)
{
mySocketIO.Close();
mySocketIO = null;
}
try
{
mySocket.Close();
}
catch
{
// We're closing.. don't worry about it
}
}
public void SendMessage(int MessageNumber, int MessageType, string Message)
{
if (mySocket != null && mySocketIO != null)
{
try
{
mySocketIO.SendMessage(MessageNumber, MessageType, Message);
}
catch
{
// mySocketIO disposed inbetween check and call
}
}
else
{
// Raise socket faulted event
if (ccSocketFaulted != null)
ccSocketFaulted(this);
}
}
}
}
Some useful links:
This is where I started:
http://vadmyst.blogspot.com.au/2008/01/how-to-transfer-fixed-sized-data-with.html
http://vadmyst.blogspot.com.au/2008/03/part-2-how-to-transfer-fixed-sized-data.html
And..
C# Sockets and Multithreading
Cause a connected socket to accept new messages right after .BeginReceive?
http://nitoprograms.blogspot.com.au/2009/04/tcpip-net-sockets-faq.html
http://www.codeproject.com/Articles/83102/C-SocketAsyncEventArgs-High-Performance-Socket-Cod
I can't post my entire solution just now; there is a flaw in my server code I need to debug; plus there are parts which my employer may not want published. But i based my code on what Vadym had for variable length messages.
When a server gets ready to accept TCP connections, it creates a new TCP socket, Bind() it to a port and uses the Listen() method. When a connection request comes in, the Listen() method returns a new socket that the server and client use for communication. The server and client can pass data back and forth using Send() and Receive() at this point. If the client disconnects, the server's Receive() terminates with 0 bytes of data.
If you want to wait for another connection request once you've accepted the first connection (i.e., while you are interacting with the first client) this can be done. At this point, you'll need to use something like threads or asynchronous methods so you can handle more than one connection. Basically, you will be able to Accept() connection requests from your listening socket.
Mike
I have a tcp connection and two threads to handle sending and receiving respectively. Sometimes the receiving thread can not receive any data after a few minutes the program started,then get a Timeout error from the Receive() method. But Wireshark shows me there is data on the wire and because the program stop receiving, the receiving window size decrease to zero.
Seems like this happens more frequently on my laptop which is a windows 7 running by Parallels on Mac OS X.
class Test
{
public static string Host { get; set; }
public static int Port { get; set; }
public static Action<Exception> ErrorHandler { get; set; }
private Socket socket;
private object sendSync;
private Thread recvThread;
private Thread sendThread;
private Thread connectThread;
private readonly int RECEIVETIMOUT = 20 * 1000;
private readonly int MAXCONNECTATTEMPTINTERVAL = 27;
private int connectingAttempt = 0;
private ManualResetEvent sendReadyEvent;
private ManualResetEvent receiveReadyEvent;
private ManualResetEvent sendStoppedEvent;
private ManualResetEvent receiveStoppedEvent;
private Queue<byte[]> waitingRequests;
private Test()
{
sendSync = new object();
waitingRequests = new Queue<byte[]>();
sendReadyEvent = new ManualResetEvent(false);
receiveReadyEvent = new ManualResetEvent(false);
sendStoppedEvent = new ManualResetEvent(true);
receiveStoppedEvent = new ManualResetEvent(true);
sendThread = new Thread(this.Send);
sendThread.IsBackground = true;
sendThread.Start();
recvThread = new Thread(this.Receive);
recvThread.IsBackground = true;
recvThread.Start();
connectThread = new Thread(this.Connect);
connectThread.IsBackground = true;
connectThread.Start();
callbackThread = new Thread(this.callback);
callbackThread.IsBackground = true;
callbackThread.Start();
}
private static Test instance = null;
public static Test GetInstance()
{
if(instance == null)
instance = new Test();
return instance;
}
private void Connect()
{
while (true)
{
try
{
sendStoppedEvent.WaitOne();
receiveStoppedEvent.WaitOne();
socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
socket.ReceiveTimeout = RECEIVETIMOUT;
var ip = Dns.GetHostAddresses(Host)[0];
var endPoint = new IPEndPoint(ip, Port);
socket.Connect(endPoint);
sendStoppedEvent.Reset();
receiveStoppedEvent.Reset();
startSend();
startReceive();
}
catch (SocketException e)
{
var waitSecond = (int)Math.Pow(3, connectingAttempt);
if (waitSecond >= MAXCONNECTATTEMPTINTERVAL)
{
waitSecond = MAXCONNECTATTEMPTINTERVAL;
if(ErrorHandler !=null)
ErrorHandler(e);
}
Thread.Sleep(waitSecond * 1000);
connectingAttempt++;
}
}
}
public void Send(byte[] request)
{
lock (sendSync)
{
waitingRequests.Enqueue(request);
Monitor.Pulse(sendSync);
}
}
private void Send()
{
while (true)
{
sendReadyEvent.WaitOne();
byte[] bytes;
lock (sendSync)
{
if (waitingRequests.Count == 0)
Monitor.Wait(sendSync)
bytes = waitingRequests.Dequeue();
}
int i = 0;
while (i < bytes.Length)
{
try
{
i += socket.Send(bytes, i, bytes.Length - i, SocketFlags.None);
}
catch (SocketException e)
{
stopSend();
break;
}
catch (ObjectDisposedException e)
{
stopSend();
break;
}
}
}
}
private void stopSend()
{
socket.Close();
sendReadyEvent.Reset();
sendStoppedEvent.Set();
}
private void startSend()
{
sendReadyEvent.Set();
}
private int totalReceived = 0;
private int recevied = 0;
private void Receive()
{
int RECVBUFFERSIZE = 1024 * 1024 * 2;
byte[] recvBuffer = new byte[RECVBUFFERSIZE];
while (true)
{
receiveReadyEvent.WaitOne();
try
{
recevied = socket.Receive(recvBuffer, totalReceived, 1024, SocketFlags.None);
if (recevied == 0)
stopReceive();
totalReceived += recevied;
//parse data
......
}
catch (SocketException e)
{
stopReceive();
}
catch (ObjectDisposedException e)
{
stopReceive();
}
}
}
private void stopReceive()
{
totalReceived = 0;
recevied = 0;
socket.Close();
receiveReadyEvent.Reset();
receiveStoppedEvent.Set();
}
private void startReceive()
{
receiveReadyEvent.Set();
}
}
Here is the Wireshark dump
No. Time Source Destination Protocol Length Info
4850 1971.053146 client server TCP 90 netview-aix-3 > autodesk-nlm [PSH, ACK] Seq=7969 Ack=188674 Win=232 Len=36
No. Time Source Destination Protocol Length Info
4851 1971.077669 server client TCP 286 [TCP Window Full] autodesk-nlm > netview-aix-3 [PSH, ACK] Seq=188674 Ack=7969 Win=28544 Len=232
No. Time Source Destination Protocol Length Info
4852 1971.077672 server client TCP 60 autodesk-nlm > netview-aix-3 [ACK] Seq=188906 Ack=8005 Win=28544 Len=0
No. Time Source Destination Protocol Length Info
4853 1971.077766 client server TCP 189 [TCP ZeroWindow] netview-aix-3 > autodesk-nlm [PSH, ACK] Seq=8005 Ack=188906 Win=0 Len=135