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TcpClient hangs

I am working on a simple Client to send data to a server at my office. I tested the code locally on my computer using a server called TCPServer, I connect, send data, receive reply, disconnect, send again, rinse and repeat, it all works perfectly, but when I connect to office and do the same thing it connects fine, I can connect/disconnect forever, but when I send data it just hangs. Nothing is received in the log at the office. I can't send a single byte there.
Seems like a firewall issue doesn't it.
But I can run an older program I wrote years ago in Delphi (pascal), and it connects and sends the same data over without issue, same port, everything, so the problem is not a firewall issue. Thoughts on this? Here is the basic code layout.
Connect Button
Disconnect Button
Send Button
At the top of the class I declare the TcpClient Variable
public TcpClient m_client = new TcpClient();
In the _Click for Connect Button and Disconnect Button I have code to connect to server and set some indicators etc
private void ConnectButton_Click(object sender, EventArgs e)
{
string address = FixIP(IPAddressMaskedTextBox.Text);
int Port = Convert.ToInt32(PortNumberMaskedTextBox.Text);
Control control = (Control)sender;
String name = control.Name;
try
{
switch (name)
{
case ("ConnectButton"):
//Connect to server
connect(address, Port);
if (m_client.Connected)
{
SingleConnectionRichTextBox.Clear();
ConnectedLightButton.BackColor = Color.Lime;
SingleConnectionRichTextBox.Text += "Connected at IP " + address + " and Port " + Port.ToString() + "\r\n";
}
break;
case ("DisconnectButton"):
if (m_client.Connected)
{
SingleConnectionRichTextBox.Text += "Connection Terminated\r\n";
ConnectedLightButton.BackColor = Color.Red;
m_client.Client.Disconnect(false);
m_client = new TcpClient();
}
break;
}
}
catch (Exception err)
{
MessageBox.Show(err.ToString());
}
}
public void connect(string address, int port)
{
try
{
if (!m_client.Connected)
{
ConnectedLightButton.BackColor = Color.Yellow;
SingleConnectionRichTextBox.Text += "Attempting to Connect...\r\n";
m_client.Connect(address, port);
}
else
{
SingleConnectionRichTextBox.Text += "Connection Failed...\r\n";
ConnectedLightButton.BackColor = Color.Red;
throw new Exception("Connect: Already connected\r\n");
}
}
catch (Exception err)
{
MessageBox.Show(err.ToString());
}
}
The Send button has it's own event, mostly because when connecting to office it can take a minute for sockets to be created etc.
private void SendButton_Click(object sender, EventArgs e)
{
try
{
if (m_client.Connected)
{
string completeString = "";
for (int cnt = 0; cnt < SingleSendRichTextBox.Lines.Count() - 1; cnt++)
{
string aLine = Regex.Replace(SingleSendRichTextBox.Lines[cnt], #"\e\[(\d+;)*(\d+)?[ABCDHJKfmsu]", "");
if (cnt == 0)
{
//First line gets Start Block, plus a CR on end
aLine = (char)0x0B + aLine + (char)0x0D;
}
else if (cnt == (SingleSendRichTextBox.Lines.Count() -1))
{
//Last line gets CR + End Block + CR on end
aLine += (char)0x0D + (char)0x1C + (char)0x0D;
}
else
{
//All middle lines get CR on end
aLine += (char)0x0D;
}
//MessageBox.Show("Sending line# " + cnt.ToString() + " = " + aLine);
completeString += aLine;
}
Byte[] data = Encoding.ASCII.GetBytes(completeString);
WriteBytes(data);
ReadAllBytes();
}
else
{
MessageBox.Show("Nothing is connected currently...");
}
}
catch (Exception err)
{
MessageBox.Show(err.ToString());
}
}
public void WriteBytes(Byte[] data)
{
try
{
if ((m_client.Connected)&&(data.Count() > 0))
{
// Get access to network stream
NetworkStream stm = m_client.GetStream();
stm.Write(data, 0, data.Length);
stm.Flush();
//MessageBox.Show("Data Sent, length = " + data.Length.ToString());
}
else
{
MessageBox.Show("Either we are not connected, or there is no data to send!!");
}
}
catch (Exception err)
{
MessageBox.Show(err.ToString());
}
}
public void ReadAllBytes()
{
try
{
// Buffer to store the response bytes.
Byte[] readdata = new Byte[256];
// String to store the response ASCII representation.
String responseData = String.Empty;
NetworkStream stm = m_client.GetStream();
// Read the first batch of the TcpServer response bytes.
Int32 bytes = stm.Read(readdata, 0, readdata.Length);
responseData = Encoding.ASCII.GetString(readdata, 0, bytes);
SingleReplyRichTextBox.Text += responseData + "\r\n";
}
catch (Exception err)
{
MessageBox.Show(err.ToString());
}
}
Does anything in here raise a red flag that is obvious? I tried Stream VS NetworkStream. I tried turning off the Reply listener. I took this code and combined it all into one function, and moved the TcpClient creation over to a different Class as static so I could create it in each function, but while all of these worked fine locally, nothing works connecting to office. It won't send a single byte. I set m_client as static at the top too, works fine locally, not to office.
Is GetStream failing maybe? or its sending the data on a different socket?

use a Task and cancellation token to cancel the task. Don't init a "new" TCPclient. In the background the TCPclient will be not closed (socket-timeout of .net)
Use try catches to see the exception and add the log to the conversation to make it more clear pls

Stream for sending byte-arrays and strings (for network)

I'm searching for a Streamclass which contains:
- a method for sending/receiving a byte-array
- a method for sending/receiving a string
The only Class I've found was NetworkStream. But the disadvantage with the NetworkStream-Class is, that if i want sending a string, i must befor convert this string into a byte-array and send this byte-array, because there is no method for sending strings directly.
And on the other side classes like Streamwriter have methods for sending/receiving strings, but there have no methods for sending/receiving a byte-array.
And if i try to combine these two Streamclasses like this:
TcpClient clientConnection = new TcpClient();
NetworkStream nws = clientConnection.GetStream();
StreamWriter sw = new StreamWriter(nws);
sw.writeLine("ABC");
sw.Flush();
nws.Write(byteArray, 0, lengthToSend);
i get a lot of strange errors (like byteArray will not receive on the other side completly), because i'm using here the same one stream in two different ways.
So, must i used NetworkStream-Class for my plan or exists there a better way?

I had the same problem,and the point is that the other side doesnt know what you are sending byte array or string so what i did is putting a header for each msg specially when dealing with serious server/client application coz you will have multiple data (user info, requesting info,replying info .. etc)
i am using streamwriter to send and streamreader to receive but i am also using threads
the connection remains open as long as the client is connected so i declare them once
here is a full example of my codes
public class Client
{
private StreamWriter swSender;
private StreamReader srReceiver;
private TcpClient tcpServer;
private Thread thrMessaging;
private string UserName = "UK";
private byte Tries = 0;
private bool Connected = false;
public void Connect()
{
if (!Connected)
{
IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName());
string User = localIPs[0].ToString();
string ServIP = "127.0.0.1";//change this to your server ip
InitializeConnection(ServIP, User);
}
else
{
CloseConnection("Disconnected at user's request.");
}
}
private void InitializeConnection(string ServIp, string User)
{
IPAddress ipAddr = IPAddress.Parse(ServIp);
tcpServer = new TcpClient();
try
{
tcpServer.Connect(ipAddr, 1986);//change that 1986 to your server port
}
catch
{
if (Connected) CloseConnection("");
MessageBox.Show("Connecteing to " + ServIp + "\r\nServer is Down ... Try nomber " + Tries); return;
}
Connected = true;
UserName = User;
swSender = new StreamWriter(tcpServer.GetStream());
swSender.WriteLine(User);
swSender.Flush();
thrMessaging = new Thread(new ThreadStart(ReceiveMessages));
thrMessaging.Start();
}
private void ReceiveMessages()
{
srReceiver = new StreamReader(tcpServer.GetStream());
string ConResponse = srReceiver.ReadLine();
if (ConResponse[0] == '1')
{
}
else
{
string Reason = "Not Connected: ";
Reason += ConResponse.Substring(2, ConResponse.Length - 2);
return;
}
while (Connected)
{
try
{
string NewMsg = srReceiver.ReadLine();
if (NewMsg != null && NewMsg != "")
PacketHandler.HandlePacket(NewMsg, this);
}
catch { }
}
}
public void CloseConnection(string Reason)
{
try
{
Connected = false;
swSender.Close();
srReceiver.Close();
tcpServer.Close();
}
catch { }
}
public void SendMessage(string Msg)
{
if (Msg.Length >= 1)
{
try
{
Tries++;
swSender.WriteLine(Msg);
swSender.Flush();
Tries = 0;
}
catch
{
if (Tries < 5)
{
try
{
CloseConnection("No connection made");
Connect();
}
catch { }
SendMessage(Msg);
}
else { MessageBox.Show("Connecting to server faild for 5 tries"); Tries = 0; }
}
}
}
then at the packet handler i do my handling to check what kind of data the client received
something like this
public static void HandlePacket(string MsgRec, Client Client)
{
string[] Info = MsgRec.Split('|');
string Type = Info[0];
if (Type == "")
{
return;
}
string subtype = Info[1];
int TLen = Type.Length + subtype.Length + 2;
string Data = MsgRec.Remove(0, TLen);//this is the main data the server sent
ushort PacketType = ushort.Parse(Type);
ushort SubType = ushort.Parse(subtype);
switch ((Structs.PacketType)PacketType)
{
case Structs.PacketType.Login:
{
//do your stuff here
break
}
case Structs.PacketType.Image:
{
//convert the Data back to byte array then get the image out from it
break
}
case Structs.PacketType.ByteArray:
{
//convert the Data back to byte array
break
}
}
}
i know its kinda messy and not the perfect way to do it , but it works for me
and remember that at the other side when sending something you need to add the packet type and subtype , or just any header with any splitter if u doin something simple
Finally : i think using Sockets and packets would be much easier if u are sending small packets length

Chat service application

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

C# UDP packetloss though all packets arrive (WireShark)

As the title says I have a problem with UDP in C#.
I'm trying to build a library for the rcon protocol of the game DayZ.
My problem is that I dont receive every packet I should receive.
After sending a command the server replies with an split answer. The packet header contains the total packet count and the index of the current packet.
Now if I should get 17 packets I only get 8-15 packets in my application.
After testing with WireShark I know now that all packages arrive on my computer. They just dont get recognized by my application or something like that.
My Actual Question is:
Is it possible to prevent losing the packages between my network card and my application? or
Why does that happen?
Here is my current code. Its pretty dirty because I ripped it apart after not working as expected:
private Socket _udpClient;
private Thread _receiverThread;
private Thread _workerThread;
private Queue<byte[]> _packetQueue;
private PacketBuffer[] MessageBuffer;
private byte SenderSequence = 0;
private IPEndPoint connection;
public RCon(IPAddress ip, int port)
{
connection = new IPEndPoint(ip, port);
_udpClient = new Socket(connection.Address.AddressFamily, SocketType.Dgram, ProtocolType.Udp);
_udpClient.Connect(connection);
MessageBuffer = new PacketBuffer[256];
_packetQueue = new Queue<byte[]>();
_receiverThread = new Thread(new ThreadStart(ReceiveCallback));
_receiverThread.IsBackground = true;
_receiverThread.Priority = ThreadPriority.AboveNormal;
_receiverThread.Start();
_workerThread = new Thread(new ThreadStart(WorkerCallback));
_workerThread.IsBackground = true;
_workerThread.Start();
}
public void Login(string password)
{
LoginPacket packet = new LoginPacket(password);
_udpClient.Send(packet.Bytes);
}
public void SendCommand(string command)
{
CommandPacket packet = new CommandPacket(SenderSequence, command);
SenderSequence++;
_udpClient.Send(packet.Bytes);
}
private void ReceiveCallback()
{
while (true)
{
byte[] buffer = new byte[1036];
if (_udpClient.Receive(buffer) > 0)
_packetQueue.Enqueue(buffer);
}
}
private void WorkerCallback()
{
while (true)
{
if (_packetQueue.Count > 0)
{
byte[] buffer = _packetQueue.Dequeue();
if (buffer != null)
{
try
{
Packet receivedPacket = Packet.ParseIncoming(buffer);
OnPacketReceived(new PacketReceivedEventArgs(receivedPacket));
switch (receivedPacket.Type)
{
case PacketType.Message:
OnMessageReceived(new MessageReceivedEventArgs(receivedPacket.Content));
MessageCallbackPacket packet = new MessageCallbackPacket(receivedPacket.SequenceNumber);
_udpClient.Send(packet.Bytes);
break;
case PacketType.CommandCallback:
if (MessageBuffer[receivedPacket.SequenceNumber] == null)
MessageBuffer[receivedPacket.SequenceNumber] = new PacketBuffer(receivedPacket);
else
MessageBuffer[receivedPacket.SequenceNumber].AddPacket(receivedPacket);
if (MessageBuffer[receivedPacket.SequenceNumber].IsComplete)
OnCommandCallback(new CommandCallbackEventArgs(MessageBuffer[receivedPacket.SequenceNumber].GetContent()));
break;
}
}
catch (ArgumentException) { }
catch (OverflowException) { }
catch (FormatException) { }
}
}
}
}

This is usually because you are not consuming your datagrams fast enough, so in-kernel socket buffer gets full and the network stack starts dropping newly arriving packets. Some points:
Increase the receive buffer on the socket,
Don't acquire locks on every iteration - read as much as you can, then put data into the queue,
Consider non-blocking approach instead of threads.

C# Networking : Server hangs after receiving more than 65535 bytes

UPDATE:
Due to problems with the admins here on Stackoverflow, I have posted a very trimmed-down version of the same problem on MSDN forum. This text below used MyNetworking.dll, but that is not the problem. Here is a very slimmed Client-Server thing and the problem is exactly the same. Feel free to try it out =)
http://social.msdn.microsoft.com/Forums/en-US/netfxnetcom/thread/d3d33eb9-7dce-4313-929e-a8a63d0f1e03
/UPDATE
So, I have a strange error.
Normally, we have a DLL that handles our networking. Lets call that MyNetworking.dll. We use it everywhere in our servers and clients and have done so for 5 years. I haven't had a problem with it, until now.
I have an "XMLPoller", that reads XML from a MySQL database, serializes that into a byte[] array and sends it over the network. These particular XML messages is 627 bytes in serialized form.
The XMLPoller connects to a port on a "remote server" (that happens to be localhost) and sends the packets, one at a time. At exactly packet nbr 105 the connection is closed. 104 packets are sent from XMLPoller and received by the Server. 104 x 627 = 65208 bytes. But packet 105, when the total number of bytes sent would be 65835 the connection is closed with this error:
System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
This is the error on the server. However, I have stepped through the XMLPoller (client), and I see when the last 627 bytes are sent (thus sending up til 65835 bytes) and I see no errors on the client, it passes sending without problems.
UPDATE 20:15 SWEDISH TIME
I also get this error in the Client when I debug a little more:
Unable to read data from the transport connection: An established connection was aborted by the software in your host machine.
I think I have confirmed that it is in the Client the error exists. I am stepping through the code and before any Exceptions are caught on the server, I get an exception on the Client as stated above.
/ENDUPDATE
It seems to me that the Server never receives it, getting the error above. The server gets the connection closed because of something happening on the Client. However, the error on the client is in TCPInput; the stream reading data is dead for some reason?
I am not buffering anything in MyNetworking.dll.
When I get a new connection on a Socket (on the Server), I do this code:
public void setConnected(Socket thisClient)
{
NetworkStream stream = new NetworkStream(thisClient);
socket = thisClient;
output = new TCPOutput(stream, outputHandler,this);
remoteIP = this.socket.RemoteEndPoint.ToString();
changeState(State.Connected);
try
{
stream.BeginRead(inputBuffer, 0, 5000, new AsyncCallback(OnDataReceived), null);
}
catch (Exception e)
{
this.disconnect();
}
}
and then, the OnDataReceived method (where the data is actually received):
public void OnDataReceived(IAsyncResult asyn)
{
int nbrRead = 0;
byte[] tmp = null;
try
{
nbrRead = stream.EndRead(asyn);
tmp = new byte[nbrRead];
}
catch (Exception e)
{
// *** HERE IS WHERE THE EXCEPTION IS CAUGHT ***
System.Diagnostics.Debugger.Log(0, "Bla1", e.ToString());
this.disconnect();
}
if (nbrRead > 0)
{
try
{
Array.Copy(inputBuffer, 0, tmp, 0, nbrRead);
}
catch(Exception e)
{
System.Diagnostics.Debugger.Log(0, "Bla2", e.ToString());
this.disconnect();
}
preProcessMessage(tmp);
try
{
stream.BeginRead(inputBuffer, 0, 5000, new AsyncCallback(OnDataReceived), new object());
}
catch(Exception e)
{
System.Diagnostics.Debugger.Log(0, "Bla3", e.ToString());
this.disconnect();
}
}
else
this.disconnect();
}
Right now Im sort of clueless as to what is going on... Any ideas?
UPDATE 1:
Client code for sending data:
public bool sendData(byte[] data)
{
if(this.state == State.Connected)
{
if (data != null && data.Length > 0)
{
try
{
//data = Crypto.Encrypt("a1s2d3", data);
outputStream.Write(data, 0, data.Length);
}
catch(Exception e)
{
System.Diagnostics.Debug.WriteLine("ClientHandler.sendData> " + e.ToString());
}
//parent.outDataLog(data.Length);
}
}
return true;
}
Update 2
I tried to do a Flush on the outgoing stream from the client - no effect:
public bool sendData(byte[] data)
{
if(this.state == State.Connected)
{
if (data != null && data.Length > 0)
{
try
{
//data = Crypto.Encrypt("a1s2d3", data);
outputStream.Write(data, 0, data.Length);
outputStream.Flush();
}
catch(Exception e)
{
System.Diagnostics.Debug.WriteLine("ClientHandler.sendData> " + e.ToString());
}
//parent.outDataLog(data.Length);
}
}
return true;
}
UPDATE 3: Posting more code as per request
This code is old and not the pretties in the world, I know. But it has been working very well for 5 years so =)
ClientHandler.cs (what the actual Client is using for sending etc)
using System;
using System.Net.Sockets;
using System.Net;
using System.Threading;
namespace tWorks.tNetworking.tNetworkingCF
{
/// <summary>
/// Summary description for connectionHandler.
/// </summary>
public class ClientHandler
{
#region Fields (17) 
string address;
Connector connector;
DataHandler dataHandler;
int id;
TCPInput input;
int interval;
string localAddress;
IPEndPoint localPoint;
int localPort;
NetworkStream outputStream;
public TTCPClientInterface parent;
int port;
tWorks.tNetworking.Protocol.Protocol protocol;
bool reconnect;
string remoteIP;
Socket socket;
public State state;
#endregion Fields 
#region Enums (1) 
public enum State {Disconnected,Connecting,Connected}
#endregion Enums 
#region Constructors (4) 
public ClientHandler(int id, TTCPClientInterface parent, Socket socket, tWorks.tNetworking.Protocol.Protocol protocol)
{
this.id=id;
this.parent = parent;
this.protocol = protocol;
dataHandler = new DataHandler(protocol, this);
setConnected(socket);
}
public ClientHandler(int id, TTCPClientInterface parent, Protocol.Protocol protocol)
{
this.id=id;
this.parent = parent;
this.protocol = protocol;
dataHandler = new DataHandler(protocol, this);
state = State.Disconnected;
}
public ClientHandler(int id, TTCPClientInterface parent, Socket socket)
{
this.id=id;
this.parent = parent;
setConnected(socket);
}
public ClientHandler(int id, TTCPClientInterface parent)
{
this.id=id;
this.parent = parent;
this.protocol = null;
changeState(State.Disconnected);
}
#endregion Constructors 
#region Delegates and Events (4) 
// Delegates (2) 
public delegate void ConnectionLostDelegate(string message);
public delegate void exceptionDelegate(Exception ex);
// Events (2) 
public event exceptionDelegate ConnectionFailed;
public event ConnectionLostDelegate ConnectionLostEvent;
#endregion Delegates and Events 
#region Methods (17) 
// Public Methods (16) 
public void connect(string address, int port, int retryInterval, bool reestablish)
{
System.Random rand = new Random();
localPort = rand.Next(40000, 60000);
IPAddress localIP = Dns.GetHostEntry(Dns.GetHostName()).AddressList[0]; // new IPAddress(Dns.GetHostByName(Dns.GetHostName()).AddressList[0].Address);
connect(address, port, retryInterval, reestablish, localIP.ToString(), localPort);
}
/// <summary>
/// Will connect to the address and port specified. If connection failed a new attempt will be made according to the Interval parameter.
/// If connection is lost attempts to reastablish it will be made if Reestablish is set to true.
/// </summary>
/// <param name="address"></param>
/// <param name="port"></param>
/// <param name="retryInterval"></param>
/// <param name="reestablish"></param>
public void connect(string address, int port, int retryInterval, bool reestablish, string localAddress, int localPort)
{
this.reconnect = reestablish;
this.address = address;
this.port = port;
this.interval = retryInterval;
this.localAddress = localAddress;
this.localPort = localPort;
changeState(State.Connecting);
connector = new Connector(address, port, this, interval, localPoint, reestablish);
connector.Connect();
}
public void disconnect()
{
reconnect = false;
if (connector != null)
{
connector.stopConnecting();
}
setDisconnected();
}
public void dispose()
{
}
public void failedConnect(Exception e)
{
if (ConnectionFailed != null)
ConnectionFailed(e);
}
public int getID()
{
return this.id;
}
public string getIP()
{
return remoteIP;
}
public bool isConnected()
{
return this.state == State.Connected;
}
public void outDataLog(int nbrBytes)
{
parent.outDataLog(nbrBytes, id);
}
public void preProcessMessage(byte[] data)
{
//data = Crypto.Decrypt("a1s2d3", data);
if(protocol != null)
dataHandler.addData(data);
else
processMessage(data);
}
public void processMessage(byte[] data)
{
parent.processMessage(data,this);
}
public bool sendData(byte[] data)
{
if(this.state == State.Connected)
{
if (data != null && data.Length > 0)
{
try
{
//data = Crypto.Encrypt("a1s2d3", data);
outputStream.Write(data, 0, data.Length);
outputStream.Flush();
}
catch(Exception e)
{
System.Diagnostics.Debug.WriteLine("ClientHandler.sendData> " + e.ToString());
}
//parent.outDataLog(data.Length);
}
}
return true;
}
public void setConnected(Socket thisClient)
{
socket = thisClient;
outputStream = new NetworkStream(thisClient);
input = new TCPInput(outputStream, this);
remoteIP = this.socket.RemoteEndPoint.ToString();
changeState(State.Connected);
}
public void setDisconnected()
{
try
{
if (this.state == State.Connected)
{
changeState(State.Disconnected);
//socket.Shutdown(SocketShutdown.Both);
socket.Close();
}
}
catch { }
if (reconnect)
this.connect(address, port, interval, true, localAddress, localPort);
}
public void stopConnect()
{
connector.stopConnecting();
changeState(State.Disconnected);
}
public override string ToString()
{
string returnString = "(D)";
if(this.state == State.Connected)
returnString = this.getIP();
return returnString;
}
// Private Methods (1) 
private void changeState(State state)
{
if (this.state == State.Connected && state == State.Disconnected)
{
if (ConnectionLostEvent != null)
ConnectionLostEvent("Uppkoppling bröts.");
}
this.state = state;
parent.connStateChange(this);
}
#endregion Methods 
}
}
This is TCPInput.cs that is listening on incoming data and forwarding that to the ClientHandler (seen above):
using System;
using System.Net.Sockets;
using System.Net;
using System.Threading;
namespace tWorks.tNetworking.tNetworkingCF
{
public class TCPInput
{
NetworkStream stream;
ClientHandler client;
public TCPInput(NetworkStream nS, ClientHandler client)
{
stream = nS;
this.client = client;
Thread t = new Thread(new ThreadStart(run));
t.IsBackground = true;
t.Name = "TCPInput";
t.Start();
}
public void run()
{
bool continueRead = true;
byte[] readBuffer = new byte[32768];
byte[] receivedBuffer = null;
int nbrBytesRead = 0;
int receivedBufferPos = 0;
while(continueRead)
{
try
{
nbrBytesRead = 0;
nbrBytesRead = stream.Read(readBuffer, 0, 10000);
receivedBuffer = new byte[nbrBytesRead];
}
catch (Exception e)
{
System.Diagnostics.Debug.WriteLine("TCPInput> Exception when stream.Read: " + e.ToString());
continueRead = false;
}
if(nbrBytesRead > 0)
{
try
{
Array.Copy(readBuffer, 0, receivedBuffer, receivedBufferPos, nbrBytesRead);
}
catch (Exception e)
{
System.Diagnostics.Debug.WriteLine("TCPInput> Exception when Array.Copy: " + e.ToString());
continueRead = false;
}
client.preProcessMessage(receivedBuffer);
}
else
{
// *** I can break here, the nbrOfBytes read is 0 when this whole thing explodes =)
System.Diagnostics.Debug.WriteLine("TCPInput> Number of bytes read == 0! Setting continueRead = false");
continueRead = false;
}
}
client.setDisconnected();
}
}
}

The problem is in your other code, the 'client'. It closes the connection after sending all the 'packets'. You must wait until the server has received all of them. A simple approach, beyond negotiating it explicitly, is to wait for the server to close the connection.

That number ("thus sending up til 65835 bytes") is magically close to 2^16-1 (65535) -- looks like just one packet over!
(I'm assuming it's just the larger size that made things go kaboom! -- this can be tested reliably.)
I suspect there is an unsigned 16-bit variable used (in the library) where you need something with more range. Perhaps you can "empty" the internals of the library periodically or perform the operation in multiple connection? (Okay, just trying to throw out some 'quick hack' ideas :-)

So, after much testing and discussing with my partner-in-crime we found out that instead of using port 21 and taking for example port 22 - the problem goes away.
I have no idea why it behaves like this, but it does...

You post raises questions for me. Like why are you choosing well known ports for this service? I don't believe in coincidences and suspect your use of the term "partner-in-crime" may have more truth then I would care to be associated with.
Then also I am wondering why you assume a Windows bug and not one in the MyNetowrking.dll. Sure, you have been using this for five years. But it still hasn't had the level of vetting that Microsoft gives their code.