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C# client socket multiple send and receive

I am using sockets for TCP-IP connection and I would like to establish simple system send-receive from the client side.
Socket sck;
sck = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint localEndpt = new IPEndPoint(IPAddress.Parse("123.123.123.1"), 12345);
try
{
sck.Connect(localEndpt);
}
catch
{
Console.Write("Unable to Connect");
}
while (true)
{
Console.WriteLine("Enter Text");
string sendtext = Console.ReadLine();
byte[] Data = Encoding.ASCII.GetBytes(sendtext);
sck.Send(Data);
Console.WriteLine("Data Sent!");
byte[] bytesReceived = new byte[sck.ReceiveBufferSize];
int bytes = 0;
String strReceived = "";
int dataAvailable = 0;
while (dataAvailable == 0 || dataAvailable != sck.Available)
{
dataAvailable = sck.Available;
Thread.Sleep(100); // if no new data after 100ms assume transmission finished
}
if (sck.Available > 0)
{
bytes = sck.Receive(bytesReceived, bytesReceived.Length, 0);
strReceived+=Encoding.ASCII.GetString(bytesReceived, 0, bytes);
}
Console.WriteLine("Received from server: " + strReceived);
}
Console.Read();
The problem is that first requests goes throught but the second does not, because socket is not available anymore (socket "Availabe" attribute value is 0). What am I doing wrong? What would be the easiest way to establish multiple send-recieve requests (in order)?

This code works fine for me
private List<Socket> _clients = new List<Socket>();
private Thread _dataReceiveThread;
private bool _isConnected;
private void DataReceive()
{
while (_isConnected)
{
List<Socket> clients = new List<Socket>(_clients);
foreach (Socket client in clients)
{
try
{
if (!client.Connected) continue;
string txt = "";
while (client.Available > 0)
{
byte[] bytes = new byte[client.ReceiveBufferSize];
int byteRec = client.Receive(bytes);
if (byteRec > 0)
txt += Encoding.UTF8.GetString(bytes, 0, byteRec);
}
if (!string.IsNullOrEmpty(txt))
/* TODO: access the text received with "txt" */
}
catch (Exception e)
{
Exception_Handler(e);
}
}
}
}
Just run this code to get started
_isConnected = true;
_dataReceiveThread = new Thread(DataReceive);
_dataReceiveThread.Start();
Update list box in Cross thread:
This code can be placed in the comment section.
myListBox1.Invoke((Action)(() => { myListBox1.Items.Add(txt) }));

Socket. Available does NOT indicate whether the socket is available, but incoming data is available for reading:
https://msdn.microsoft.com/en-us/library/ee425135.aspx
Your program quits because it checks for a reply (incoming data) immediately after sending a message out. Use a Thread.Sleep before checking for data.
Maybe the message has not even been sent, because Socket.Send just places it in the network interface card's output buffer. When the socket finally sends the message, it will upare the connection state. If it got no reply (on a TCP connection), it will tell you that it is disconnected when you query the state. On UDP it will tell you nothing, because UDP is connectionless.

C# - C:stop blocking listen socket on a child thread

My program:I create 2 threads:Thread 1 with a listen socket,and thread 2 do somethings.
But thread 1 blocks program and i can not start thread 2 until listen socket on thread 1 receives data.
But i need 2 threads run at the same time,and don`t need to keep in sync between 2 threads.(but still in same program).
How to do it???
My code like this:
Thread thread1 = new Thread(new ThreadStart(a.thread1));
Thread thread2 = new Thread(new ThreadStart(b.thread2));
try
{
thread1.Start();
thread2.Start();
thread1.Join(); // Join both threads with no timeout
// Run both until done.
thread2.Join();
}
Program stop at thread 1(listen socket).
And i don't want to use non-blocking socket(I am using blocking socket).
Listen socket should block child thread,but should not block my program.

I have just recently had this self same issue and resolved it like this:
private static void StartServers()
{
for (int i = Convert.ToInt32(ConfigurationManager.AppSettings.Get("PortStart"));
i <= Convert.ToInt32(ConfigurationManager.AppSettings.Get("PortEnd"));
i++)
{
var localAddr = IPAddress.Parse(ConfigurationManager.AppSettings.Get("IpAddress"));
var server = new TcpListener(localAddr, i);
Servers.Add(server);
server.Start();
StartAccept(server);
}
}
private static void StartAccept(TcpListener server)
{
server.BeginAcceptTcpClient(OnAccept, server);
}
private static void OnAccept(IAsyncResult res)
{
var client = new TcpClient();
try
{
Console.ForegroundColor = Console.ForegroundColor == ConsoleColor.Red
? ConsoleColor.Green
: ConsoleColor.White;
var server = (TcpListener) res.AsyncState;
StartAccept(server);
client = server.EndAcceptTcpClient(res);
Console.WriteLine("Connected!\n");
var bytes = new byte[512];
// Get a stream object for reading and writing
var stream = client.GetStream();
int i;
// Loop to receive all the data sent by the client.
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
// Translate data bytes to a ASCII string.
var data = Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine("Received: {0} \n", data);
// Process the data sent by the client.
data = InterpretMessage(data);
var msg = Encoding.ASCII.GetBytes(data);
// Send back a response.
stream.Write(msg, 0, msg.Length);
Console.WriteLine("Sent: {0} \n", data);
}
}
catch (Exception exception)
{
Console.ForegroundColor = ConsoleColor.Red;
client.Close();
Console.WriteLine(exception.Message);
}
}
Basically what this does is creates an asynchronous receiving system in which you can have multiple servers listening to multiple ports simultaneously. Bearing in mind that you can only ever have one listener per port.
In your example, you can simply call the StartServers method and then directly afterwards, continue with whatever your application is doing.
In order for this to work for a single server on a single port, merely remove the looping in StartServers and configure 1 TcpListener and start it up.

Reading information from a port waits even though data available

I am having a problem sending information down a socket and receiving a response. I have a demo program which is performing correctly so I know it is not an issue with the client on the other end.
The requestData is sent and the client acts correctly and responds, but my code never exits the loop in read response.
Could the client be responding before I am listening? How can I make sure I never miss an incoming message?
networkStream = tcpClient.GetStream();
StreamWriter clientStreamWriter = new StreamWriter();
clientStreamWriter.WriteLine(requestData);
clientStreamWriter.Flush();
// Continuously read data on the socket and if it is more than just a ping, read the response.
StringBuilder sbReadBuffer = new StringBuilder();
while (true)
{
String response = readresponse(timeoutOn30Seconds);
if (response.Length > 1 && (!response.Contains("\r\n") || response.Contains(",")))
{
break;
}
}
sbReadBuffer.Append(received);
return sbReadBuffer.ToString();
readResponse:
private string readresponse(Boolean timeoutOn30Seconds)
{
// Get network stream.
DateTime lastConTime = DateTime.Now;
Int32 i = 0;
// Start listening to stream.
while (!networkStream.DataAvailable)
{
Log.W(".");
// Only check every 10ms.
Thread.Sleep(10);
// If no response in 30mins stop listening and give an offline warning.
if ((DateTime.Now - lastConTime).TotalSeconds > tcpClient.ReceiveTimeout)
{
received = "CLIENT NOT FOUND";
return received;
}
// Only check if application online every 1s.
if (i > 100)
{
if (Process.GetProcessesByName(ConfigurationManager.AppSettings["ClientName"]).FirstOrDefault() == null && Convert.ToInt32(ConfigurationManager.AppSettings["Device"]) != 680)
{
received = "CLIENT NOT FOUND";
return received;
}
i = 0;
}
i++;
}
// If data has been writted to the buffer, read it out and assign output variable and return that string for length comparison.
byte[] receiveBuffer = new byte[tcpClient.ReceiveBufferSize];
Int32 receiveCount = networkStream.Read(receiveBuffer, 0, receiveBuffer.Length);
received = new ASCIIEncoding().GetString(receiveBuffer, 0, receiveCount);
return received;
}

DataAvailable isn't a good method to know if data are coming, especially in a while loop that is surely faster than network communications.
A better way could be to use the Read method (bytes read) to know where data are available, into a timed loop; so change your while condition in this manner (and then adjust the other parts)
while (networkStream.Read(receiveBuffer, 0, receiveBuffer.Length) > 0)
{
Log.W(".");
// Only check every 10ms.
Thread.Sleep(10);
but I prefer, if possible, an async approach, so your client will be notified when data are incoming.
See this answer that use this kind of approach.
Basically set an async callback that will be fired when data are coming
public void StartListening() {
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPEndPoint localEP = new IPEndPoint(ipHostInfo.AddressList[0],11000);
Console.WriteLine("Local address and port : {0}",localEP.ToString());
Socket listener = new Socket( localEP.Address.AddressFamily,
SocketType.Stream, ProtocolType.Tcp );
try {
listener.Bind(localEP);
listener.Listen(10);
while (true) {
allDone.Reset();
Console.WriteLine("Waiting for a connection...");
listener.BeginAccept(
new AsyncCallback(SocketListener.acceptCallback),
listener );
allDone.WaitOne();
}
} catch (Exception e) {
Console.WriteLine(e.ToString());
}
Console.WriteLine( "Closing the listener...");
}
and there you can read your data
public static void acceptCallback(IAsyncResult ar) {
// Get the socket that handles the client request.
Socket listener = (Socket) ar.AsyncState;
Socket handler = listener.EndAccept(ar);
// Signal the main thread to continue.
allDone.Set();
// Create the state object.
StateObject state = new StateObject();
state.workSocket = handler;
handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(AsynchronousSocketListener.readCallback), state);
}
Here full MSDN documentation

You dont read in while loop. To clear DataAvailable flag, you have to read from networkStream.
Sample usage :
http://msdn.microsoft.com/en-us/library/system.net.sockets.networkstream.dataavailable%28v=vs.100%29.aspx

Using C# TcpClient to receive a JSON based protocol

I'm connecting to a server that talks in a JSON protocol. It sends each bit of information as a JSON object. Here are three examples.
{"from":"SERVER","code":"SERVER_OK"}
{"from":"SERVER","code":"CHAT_JOIN","data":{"room":"Lobby"}}
{"from":"SERVER","code":"PING","data":{"time":1405901428001}}
My C# code looks like this.
void Start () {
clientSocket = new TcpClient();
clientSocket.Connect("127.0.0.1", 5000);
serverStream = clientSocket.GetStream();
serverStream.BeginRead(buffer, 0, buffer.Length, ReadComplete, buffer);
}
void ReadComplete (IAsyncResult iar) {
buffer = (byte[])iar.AsyncState;
int bytesAvailable = serverStream.EndRead(iar);
string data = System.Text.Encoding.UTF8.GetString(buffer);
Array.Clear(buffer, 0, 4096);
serverStream.BeginRead(buffer, 0, buffer.Length, ReadComplete, buffer);
Debug.Log(data);
}
My debug log looks like this:
{"from":"SERVER","code":"SERVER_OK"}{"from":"SERVER","code":"CHAT_JOIN","data":{"room":"Lobby"}}
{"from":"SERVER","code":"PING","data":{"time":1405901428001}}
{"from":"SERVER","code":"PING","data":{"time":1405901433001}}
{"from":"SERVER","code":"PING","data":{"time":1405901438004}}
It looks like I can receive more than one JSON object at a time in each ReadComplete. I also assume I could receive a partial JSON object as well. What do I need to do to be able to process a single JSON object at a time? I'm guessing I have to concatenate each received chunk of data to a string and the chop off the front of it each object one at a time. I just have no idea how to go about doing that.

I ended up moving into a Thread and processing the stream one byte at a time looking for the JSON object boundaries. For each on I try to parse it and add it a Queue for the parent thread to process.
So far this seems to work without causing any threading issues with the rest of my application and has been working well with the overall performance for my needs.
// The network thread listening to the server
private void NetworkThread () {
Debug.Log("Connecting to server...");
clientSocket = new TcpClient();
clientSocket.Connect("127.0.0.1", 5000);
stream = clientSocket.GetStream();
int braces = 0;
bool inQ = false;
char lastB = ' ';
while (!stopThread) {
char b = (char)stream.ReadByte();
if (b < 0)
return;
buffer.Append((char)b);
if (b == '"' && lastB != '\\') {
inQ = !inQ;
}
else if (b == '{' && !inQ) {
braces += 1;
}
else if (b == '}' && !inQ) {
braces -= 1;
}
lastB = (char)b;
if (braces == 0) {
try {
JSONNode packet = JSONNode.Parse(buffer.ToString());
buffer = new StringBuilder();
lock (lockQueue) {
packetQueue.Enqueue(packet);
}
} catch (Exception e) {
}
}
}
}

Instat of manually reciving the data use Streamreader and it's .ReadLine() method. It looks like the server sends line for line, so it should not be a problem to read response for response.

TCP both Client and Server on the same PC

I'm trying to implement a small tcp based application in C#. I'm new to TCP programming.
The app is really simple. It's a client/server scenario, which support max 2 clients. One client will be an "external" IP, the other will be the host itself.
Everytime a client connect to the server, it begins to receive and send packets from/to the server.
I have set up a small console app which implements both TCP server side code and TCP client code.
The server use a listener binded to a specific port and wait for client connections. Once a client is connected, it spawn a new thread to handle communication with the client.
The client simply connect to the server and once the connection is estabilished it starts to receive and send pakcets.
As I said before "the host is also client of itself", but this leads to an issue. If the client send a packet to the server, both server and client claims to have received a packet. It is normal? Am I missing something?
UPDATE 2 (fixing issue)
I think I've found the issue. I need to "reset" the buffer once the send operation is done by the client
case SocketAsyncOperation.Send:
// Put in listen mode
// Buffer reset AFTER send and BEFORE receive
_receiver.SetBuffer(new byte[4096], 0, 4096);
_client.ReceiveAsync(_receiver);
break;
UPDATE 1 (adding code)
Server
public void Host()
{
_listener = new TcpListener(new IPEndPoint(IPAddress.Any, this.ConnectionPort));
_listener.Start();
this.IsListening = true;
ThreadPool.QueueUserWorkItem((state) =>
{
while (true)
{
// Blocks until a client connections occours
// If continue with no client then stop listening
try
{
TcpClient client = _listener.AcceptTcpClient();
// Add client to peer list
long assignedID = DateTime.UtcNow.Ticks;
_clients.Add(assignedID, client);
HandleClient(assignedID);
if (this.ConnectedClients == this.MaxClients)
{
_listener.Stop();
this.IsListening = false;
break;
}
}
catch
{
// Server has stop listening
_stopListen.Set();
break;
}
}
});
}
private void HandleClient(long assignedID)
{
ThreadPool.QueueUserWorkItem((state) =>
{
long clientID = (long)state;
TcpClient client = _clients[clientID];
try
{
byte[] message = new byte[4096];
byte[] buffer = new byte[4096];
int readed = 0;
int index = 0;
NetworkStream clientStream = client.GetStream();
while (true)
{
readed = clientStream.Read(message, 0, message.Length);
if (readed == 0)
{
// Client disconnected, thorw exception
throw new SocketException();
}
Array.Copy(message, 0, buffer, index, readed);
index += readed;
if (readed == 4096
&& !_packetHub.IsValidBufferData(buffer))
{
Array.Clear(buffer, 0, buffer.Length);
readed = 0;
index = 0;
continue;
}
if (_packetHub.IsValidBufferData(buffer))
{
NetPacket receivedPacket = _packetHub.DeserializePacket(buffer);
NetPacket answerPacket = null;
// Assign sender ID in case of unknown sender ID
if (receivedPacket.SenderID == NetPacket.UnknownID)
receivedPacket.SenderID = clientID;
// Handle received packet and forward answer packet
// to the client or to all other connected peers
answerPacket = HandlePacket(receivedPacket);
if (answerPacket != null)
{
if (answerPacket.RecipientID == clientID)
{
// Send answer packet to the client
SendPacket(client, answerPacket);
}
else
{
// Broadcast packet to all clients
foreach (TcpClient peer in _clients.Values)
SendPacket(peer, answerPacket);
}
}
// Reset receive packet buffer
Array.Clear(buffer, 0, buffer.Length);
readed = 0;
index = 0;
}
}
}
catch
{
System.Diagnostics.Debug.WriteLine("Network error occours!");
}
finally
{
// Close client connection
client.Close();
// Remove the client from the list
_clients.Remove(clientID);
// Raise client disconnected event
OnClientDisconnected();
}
}, assignedID);
}
Client
public void Connect()
{
if (this.ConnectionAddress == null)
throw new InvalidOperationException("Unable to connect. No server IP specified.");
_receiver = new SocketAsyncEventArgs();
_receiver.RemoteEndPoint = new IPEndPoint(this.ConnectionAddress, this.ConnectionPort);
_receiver.SetBuffer(new byte[4096], 0, 4096);
_receiver.Completed += new EventHandler<SocketAsyncEventArgs>(Socket_OperationComplete);
_client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
_client.ConnectAsync(_receiver);
}
private void Socket_OperationComplete(object sender, SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
switch (e.LastOperation)
{
case SocketAsyncOperation.Connect:
_readyToSend = true;
this.IsConnected = true;
// Once connection is estabilished, send a join packet to
// retrive server side assigned informations
JoinPacket joinPacket = (JoinPacket)NetPacket.CreatePacket(this.ClientID, NetPacket.ToHost, NetPacket.JoinPacket);
joinPacket.ClientName = this.ClientName;
joinPacket.ClientAddress = this.LocalAddress.ToString();
SendPacket(joinPacket);
break;
case SocketAsyncOperation.Receive:
_readyToSend = true;
byte[] buffer = _receiver.Buffer;
System.Diagnostics.Debug.WriteLine("Client received packet (" + _packetHub.GetBufferDataType(buffer) + ") with length of: " + buffer.Length);
if (_packetHub.IsValidBufferData(buffer))
{
NetPacket receivedPacket = _packetHub.DeserializePacket(buffer);
NetPacket answerPacket = null;
// Handle received packet and forward answer packet
// to the server
answerPacket = HandlePacket(receivedPacket);
if (answerPacket != null)
SendPacket(answerPacket);
}
else
{
_client.ReceiveAsync(_receiver);
}
break;
case SocketAsyncOperation.Send:
// Put in listen mode
_client.ReceiveAsync(_receiver);
break;
}
}
else
{
OnClientDisconnected();
System.Diagnostics.Debug.WriteLine(String.Format("Network error: {0}", e.SocketError.ToString()));
}
}

Since you are using TCP, you have to specify a port to send/listen (different for server and client). So no, it isn't normal (but it is if client and server are sending/listening on the same port).