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C# check multiple client connections

I am currently developing a one-to-many relationship between one server and many clients.
Everytime a client connects I append to the client list: clientList.Add(client);
I wrote the following code to check the "pulse" of the client connection as to see if the client is still connected and currently updating the toolStripStatusLabel1
This seems to work well when checking one connection and in addition, I added the exception cleanup() when trying to send data so that it should check at all scenarios(Feel free to give your opinion).
My question now is, how do I check the connection from multiple clients?
Please find below the reference code:
private void StartListen()
{
//Creating a TCP Connection and listening to the port
tcpListener = new TcpListener(System.Net.IPAddress.Any, 6666);
tcpListener.Start();
toolStripStatusLabel1.Text = "Listening on port 6666 ...";
int counter = 0;
appStatus = 0;
while (true)
{
try
{
client = tcpListener.AcceptTcpClient();
counter++;
clientList.Add(client);
IPEndPoint ipend = (IPEndPoint)client.Client.RemoteEndPoint;
//Updating status of connection
toolStripStatusLabel1.Text = "Connected from " + IPAddress.Parse(ipend.Address.ToString());
appStatus = 1;
th_outPutStream = new Thread(delegate () { outPutStream(client); });
th_outPutStream.Start();
th_inPutStream = new Thread(delegate () { inPutStream(client); });
th_inPutStream.Start();
th_checkConnection = new Thread(checkConnection);
th_checkConnection.Start();
}
catch (Exception err)
{
Cleanup();
}
}
}
private void checkConnection()
{
bool status = true;
while (status == true)
{
status = IsConnected();
if (status == true)
{
System.Threading.Thread.Sleep(3000); //Wait 3 seconds then try again
}
else
{
Cleanup();
}
}
}
private bool IsConnected()
{
try
{
return !(client.Client.Poll(1, SelectMode.SelectRead) && client.Client.Available == 0);
}
catch (SocketException) { Cleanup(); return false; }
}

I did this by simply creating a forloop for each client in my client list:
private void checkConnection()
{
bool status = true;
while (true)
{
for (int i = 0; i < clientList.Count; i++)
{
Debug.WriteLine(clientList.Count);
status = IsConnected(i);
if (status == true)
{
}
else
{
Cleanup(i);
}
}
System.Threading.Thread.Sleep(3000); //Wait 3 seconds then try again
}
}
private bool IsConnected(int i)
{
try
{
return !(clientList[i].Client.Poll(1, SelectMode.SelectRead) && clientList[i].Client.Available == 0);
}
catch (SocketException) { Cleanup_dep(); return false; }
}

C# - Multithreaded TCP Server/Client

I am trying to understand the correct way of how should I make good multithreaded TCP server.
Here is what I have so far:
public class WorldServer
{
public List<ServerClient> clients = new List<ServerClient>();
public int port = 8080;
public TcpListener server;
private bool serverStarted;
private int connectionIncrementor;
private MySQLConnection mySQLConnection = new MySQLConnection();
private MySqlConnection mysqlConn = null;
static void Main(string[] args)
{
WorldServer serverInstance = new WorldServer();
Console.WriteLine("Starting World Server...");
try
{
serverInstance.mysqlConn = new MySqlConnection(serverInstance.mySQLConnection.mysqlConnectionString);
serverInstance.mysqlConn.Open();
Console.WriteLine("Connected to MySQL version: " + serverInstance.mysqlConn.ServerVersion + "\n");
}
catch (Exception e)
{
Console.WriteLine("MySQL Error: " + e.ToString());
}
finally
{
if (serverInstance.mysqlConn != null)
{
serverInstance.mysqlConn.Close();
}
}
serverInstance.clients = new List<ServerClient>();
try
{
serverInstance.server = new TcpListener(IPAddress.Any, serverInstance.port);
serverInstance.server.Start();
serverInstance.StartListening();
serverInstance.serverStarted = true;
Console.WriteLine("Server has been started on port: " + serverInstance.port);
}
catch (Exception e)
{
Console.WriteLine("Socket error: " + e.Message);
}
while (true)
{
serverInstance.Update();
}
}
private void Update()
{
//Console.WriteLine("Call");
if (!serverStarted)
{
return;
}
foreach (ServerClient c in clients.ToList())
{
//Check if TCP is not null
if (c.tcp == null)
return;
// Is the client still connected?
if (!IsConnected(c.tcp))
{
c.tcp.Close();
clients.Remove(c);
Console.WriteLine(c.connectionId + " has disconnected.");
continue;
//Console.WriteLine("Check for connection?\n");
}
else
{
// Check for message from Client.
NetworkStream s = c.tcp.GetStream();
if (s.DataAvailable)
{
string data = c.streamReader.ReadLine();
if (data != null)
{
if (ValidateJSON(data))
{
Thread incomingData = new Thread(() => OnIncomingData(c, data));
incomingData.Start();
}
}
}
//continue;
}
}
}
public bool ValidateJSON(string s)
{
try
{
JToken.Parse(s);
return true;
}
catch (JsonReaderException ex)
{
Trace.WriteLine(ex);
return false;
}
}
private void OnIncomingData(ServerClient c, string data)
{
dynamic json = JsonConvert.DeserializeObject(data);
string header = json.header;
//Console.WriteLine("HEADER ID:" + json.header);
string connId = json.connectionId;
int.TryParse(connId, out int connectionId);
int characterId = 0;
Dictionary<string, string> receivedData = new Dictionary<string, string>();
if (json.data != null)
{
receivedData = json.data.ToObject<Dictionary<string, string>>();
}
if (json.data["characterId"] != null)
{
characterId = json.data["characterId"];
}
string prefix = header.Substring(0, 2);
if (prefix != "1x")
{
Console.WriteLine("Unknown packet: " + data + "\n");
}
else
{
string HeaderPacket = header.Substring(2);
switch (HeaderPacket)
{
default:
Console.WriteLine("Unknown packet: " + data + "\n");
break;
case "004":
Console.WriteLine("Test Packet"); ;
break;
}
}
//Broadcast(null, data, clients);
//Console.WriteLine(c.clientName + " has sent the following message :" + data);
}
public bool IsConnected(TcpClient c)
{
try
{
if (c != null && c.Client != null && c.Client.Connected)
{
if (c.Client.Poll(0, SelectMode.SelectRead))
{
return !(c.Client.Receive(new byte[1], SocketFlags.Peek) == 0);
}
return true;
}
else
{
return false;
}
}
catch
{
return false;
}
}
private void StartListening()
{
server.BeginAcceptTcpClient(OnConnection, server);
}
private void OnConnection(IAsyncResult ar)
{
connectionIncrementor++;
TcpListener listener = (TcpListener)ar.AsyncState;
clients.Add(new ServerClient(listener.EndAcceptTcpClient(ar)));
clients[clients.Count - 1].connectionId = connectionIncrementor;
StartListening();
//Send a message to everyone, say someone has connected!
Dictionary<string, object> SendDataBroadcast = new Dictionary<string, object>();
SendDataBroadcast.Add("connectionId", clients[clients.Count - 1].connectionId);
Broadcast("001", SendDataBroadcast, clients[clients.Count - 1].connectionId);
Console.WriteLine(clients[clients.Count - 1].connectionId + " has connected.");
}
public void Broadcast(string header, Dictionary<string, object> data, int cnnId = 0)
{
string jsonData = JsonConvert.SerializeObject(data, Formatting.Indented);
foreach (ServerClient c in clients)
{
try
{
if (header == null)
{
header = "000";
}
JsonData SendData = new JsonData();
SendData.header = "0x" + header;
SendData.data = JObject.Parse(jsonData);
SendData.connectionId = cnnId;
string JSonData = JsonConvert.SerializeObject(SendData);
//Console.WriteLine("SENDING: " + JSonData);
c.streamWriter.WriteLine(JSonData);
c.streamWriter.Flush();
}
catch (Exception e)
{
Console.WriteLine("Write error : " + e.Message + " to client " + c.connectionId);
}
}
}
public void Send(string header, Dictionary<string, object> data, int cnnId)
{
string jsonData = JsonConvert.SerializeObject(data, Formatting.Indented);
foreach (ServerClient c in clients.ToList())
{
if (c.connectionId == cnnId)
{
try
{
//Console.WriteLine("Sending...");
if (header == null)
{
header = "000";
}
JsonData SendData = new JsonData();
SendData.header = "0x" + header;
SendData.data = JObject.Parse(jsonData);
SendData.connectionId = cnnId;
string JSonData = JsonConvert.SerializeObject(SendData);
c.streamWriter.WriteLine(JSonData);
c.streamWriter.Flush();
//Console.WriteLine("Trying to send data to connection id: " + cnnId + " data:" + sendData);
}
catch (Exception e)
{
Console.WriteLine("Write error : " + e.Message + " to client " + c.connectionId);
}
}
}
}
}
public class ServerClient
{
public TcpClient tcp;
public StreamReader streamReader;
public StreamWriter streamWriter;
public int accountId;
public int connectionId;
public ServerClient(TcpClient clientSocket)
{
tcp = clientSocket;
streamReader = new StreamReader(tcp.GetStream(), false);
streamWriter = new StreamWriter(tcp.GetStream());
clientSocket.NoDelay = true;
}
}
The TCP server works. However I am really not sure if this is the best approach I can take.
Have I made the multi-threading well ? Probably not. I would like to receive advices where i can make it better.
Do I need to create a new thread on every OnIncomingData ?
Do I need to create new thread on every Send and Broadcast ?
Very often I receive error here foreach (ServerClient c in clients.ToList()). What can be the cause of it ?
What parts of the client is good to be multithreaded also aka the listening function for incoming data or the sending functions?
All advices are most welcome!

I wrote code for an OP last year that was a TCP Server and wrote to a SQL Server. I modified that code a few minutes ago to make it more general. The changes are not tested but original code worked very well. I used Asynchronous Send and Receive. I also used a fifo to send messages from the transport layer to the application layer. See code below
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Data;
using System.Data.SqlClient;
using System.Timers;
using System.Threading;
namespace TCP_Server
{
public class StateObject
{
public long connectionNumber = -1;
public Socket workSocket { get; set; }
public byte[] buffer { get; set; }
public int fifoCount { get; set; }
}
public enum PROCESS_STATE
{
ACCEPT,
READ,
PROCESS,
UNPACK
}
public enum UNPACK_STATUS
{
ERROR,
NOT_ENOUGH_BYTES,
BAD_CRC,
GOOD_MESSAGE,
DEFAULT
}
public enum PROTOCOL_NUMBER
{
LOGIN_MESSAGE,
NONE
}
class Program
{
const string IP = "127.0.0.1";
const int PORT = 8841;
const Boolean test = true;
static void Main(string[] args)
{
Server server = new Server(IP, PORT, test);
Console.WriteLine("Connection Ended");
}
}
public class Server
{
const int BUFFER_SIZE = 1024;
const string CONNECT_STRING = #"Data Source=.\SQLEXPRESS;Initial Catalog=MyDataTable;Integrated Security=SSPI;";
const string LOGIN_INSERT_COMMMAND_TEXT = "use MyTable INSERT INTO Login (TerminalID,Date) VALUES(#TerminalID,#Date)";
const string LOCATION_INSERT_COMMMAND_TEXT = "INSERT INTO MyTable (CurrTime, Message)" +
"VALUES (#CurrTime, #Message)";
static SqlConnection conn = null;
static SqlCommand cmdLogin = null;
static SqlCommand cmdLocation = null;
static long connectionNumber = 0;
//mapping of connection number to StateObject
static Dictionary<long, KeyValuePair<List<byte>, StateObject>> connectionDict = new Dictionary<long, KeyValuePair<List<byte>, StateObject>>();
//fifo contains list of connections number wait with receive data
public static List<long> fifo = new List<long>();
public static AutoResetEvent allDone = new AutoResetEvent(false);
public static AutoResetEvent acceptDone = new AutoResetEvent(false);
public enum DATABASE_MESSAGE_TYPE
{
LOGIN,
LOCATION
}
public class WriteDBMessage
{
public DATABASE_MESSAGE_TYPE message { get; set; }
}
public class WriteDBMessageLogin : WriteDBMessage
{
public DateTime date { get; set; }
public string message { get; set; }
}
public class WriteDBMessageLocation : WriteDBMessage
{
public DateTime currTime { get; set; }
public byte[] message { get; set; }
}
public static class WriteDBAsync
{
public enum Mode
{
READ,
WRITE
}
public static List<WriteDBMessage> fifo = new List<WriteDBMessage>();
public static System.Timers.Timer timer = null;
public static void WriteDatabase()
{
timer = new System.Timers.Timer(1000);
timer.Elapsed += Timer_Elapsed;
timer.Start();
}
public static WriteDBMessage ReadWriteFifo(Mode mode, WriteDBMessage message)
{
Object thisLock2 = new Object();
lock (thisLock2)
{
switch (mode)
{
case Mode.READ:
if (fifo.Count > 0)
{
message = fifo[0];
fifo.RemoveAt(0);
}
break;
case Mode.WRITE:
fifo.Add(message);
break;
}
}
return message;
}
static void Timer_Elapsed(object sender, ElapsedEventArgs e)
{
timer.Enabled = false;
WriteDBMessage row = null;
int rowsAdded = 0;
uint number = 0;
try
{
while ((row = ReadWriteFifo(Mode.READ, null)) != null)
{
switch (row.message)
{
case DATABASE_MESSAGE_TYPE.LOGIN:
cmdLogin.Parameters["#Date"].Value = ((WriteDBMessageLogin)row).date;
rowsAdded = cmdLogin.ExecuteNonQuery();
break;
}
}
}
catch (Exception ex)
{
//Console.WriteLine("Error : '{0}'", ex.Message);
}
timer.Enabled = true;
}
}
public Server(string IP, int port, Boolean test)
{
try
{
conn = new SqlConnection(CONNECT_STRING);
conn.Open();
cmdLogin = new SqlCommand(LOGIN_INSERT_COMMMAND_TEXT, conn);
cmdLogin.Parameters.Add("#TerminalID", SqlDbType.NVarChar, 8);
cmdLogin.Parameters.Add("#Date", SqlDbType.DateTime);
cmdLocation = new SqlCommand(LOCATION_INSERT_COMMMAND_TEXT, conn);
cmdLocation.Parameters.Add("#IMEI", SqlDbType.NVarChar, 50);
cmdLocation.Parameters.Add("#TrackTime", SqlDbType.DateTime);
cmdLocation.Parameters.Add("#currTime", SqlDbType.DateTime);
cmdLocation.Parameters.Add("#Longitude", SqlDbType.NChar, 50);
cmdLocation.Parameters.Add("#Lattitude", SqlDbType.NVarChar, 50);
cmdLocation.Parameters.Add("#speed", SqlDbType.Float);
}
catch (Exception ex)
{
Console.WriteLine("Error : '{0}'", ex.Message);
//Console.ReadLine();
return;
}
try
{
//initialize the timer for writing to database.
WriteDBAsync.WriteDatabase();
StartListening(IP, port, test);
// Open 2nd listener to simulate two devices, Only for testing
//StartListening(IP, port + 1, test);
ProcessMessages();
}
catch (Exception ex)
{
Console.WriteLine("Error : '{0}'", ex.Message);
//Console.ReadLine();
return;
}
}
public void StartListening(string IP, int port, Boolean test)
{
try
{
// Establish the local endpoint for the socket.
// The DNS name of the computer
// running the listener is "host.contoso.com".
IPHostEntry ipHostInfo = Dns.GetHostEntry(IP); //Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
//IPAddress local = IPAddress.Parse(IP);
IPEndPoint localEndPoint = null;
if (test)
{
localEndPoint = new IPEndPoint(IPAddress.Any, port);
}
else
{
localEndPoint = new IPEndPoint(ipAddress, port);
}
// Create a TCP/IP socket.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and listen for incoming connections.
allDone.Reset();
acceptDone.Reset();
listener.Bind(localEndPoint);
listener.Listen(100);
//login code, wait for 1st message
Console.WriteLine("Wait 5 seconds for login message");
listener.BeginAccept(new AsyncCallback(AcceptCallback), listener);
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
}
public void ProcessMessages()
{
UInt16 sendCRC = 0;
DateTime date;
int year = 0;
int month = 0;
int day = 0;
int hour = 0;
int minute = 0;
int second = 0;
KeyValuePair<List<byte>, StateObject> byteState;
KeyValuePair<UNPACK_STATUS, byte[]> status;
byte[] receiveMessage = null;
StateObject state = null;
byte[] serialNumber = null;
byte[] serverFlagBit = null;
byte[] stringArray = null;
string stringMessage = "";
byte lengthOfCommand = 0;
PROTOCOL_NUMBER protocolNumber = PROTOCOL_NUMBER.NONE;
try
{
Boolean firstMessage = true;
acceptDone.Set();
//loop forever
while (true)
{
allDone.WaitOne();
//read fifo until empty
while (true)
{
//read one connection until buffer doesn't contain any more packets
byteState = ReadWrite(PROCESS_STATE.PROCESS, null, null, -1);
if (byteState.Value.fifoCount == -1) break;
state = byteState.Value;
while (true)
{
status = Unpack(byteState);
if (status.Key == UNPACK_STATUS.NOT_ENOUGH_BYTES)
break;
if (status.Key == UNPACK_STATUS.ERROR)
{
Console.WriteLine("Error : Bad Receive Message, Data");
break;
}
//message is 2 start bytes + 1 byte (message length) + 1 byte message length + 2 end bytes
receiveMessage = status.Value;
int messageLength = receiveMessage[2];
Console.WriteLine("Status : '{0}', Receive Message : '{1}'", status.Key == UNPACK_STATUS.GOOD_MESSAGE ? "Good" : "Bad", BytesToString(receiveMessage.Take(messageLength + 5).ToArray()));
if (status.Key != UNPACK_STATUS.GOOD_MESSAGE)
{
break;
}
else
{
if (firstMessage)
{
if (receiveMessage[3] != 0x01)
{
Console.WriteLine("Error : Expected Login Message : '{0}'", BytesToString(receiveMessage));
break;
}
firstMessage = false;
}
//skip start bytes, message length. then go back 4 bytes (CRC and serial number)
serialNumber = receiveMessage.Skip(2 + 1 + messageLength - 4).Take(2).ToArray();
protocolNumber = (PROTOCOL_NUMBER)receiveMessage[3];
Console.WriteLine("Protocol Number : '{0}'", protocolNumber.ToString());
switch (protocolNumber)
{
case PROTOCOL_NUMBER.LOGIN_MESSAGE:
break;
} //end switch
}// End if
} //end while
}//end while fifo > 0
allDone.Reset();
}//end while true
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
}
static string BytesToString(byte[] bytes)
{
return string.Join("", bytes.Select(x => x.ToString("X2")));
}
static KeyValuePair<UNPACK_STATUS, byte[]> Unpack(KeyValuePair<List<byte>, StateObject> bitState)
{
List<byte> working_buffer = bitState.Key;
//return null indicates an error
if (working_buffer.Count() < 3) return new KeyValuePair<UNPACK_STATUS, byte[]>(UNPACK_STATUS.NOT_ENOUGH_BYTES, null);
int len = working_buffer[2];
if (working_buffer.Count < len + 5) return new KeyValuePair<UNPACK_STATUS, byte[]>(UNPACK_STATUS.NOT_ENOUGH_BYTES, null);
// check start and end bytes
// remove message fro workig buffer and dictionary
KeyValuePair<List<byte>, StateObject> byteState = ReadWrite(PROCESS_STATE.UNPACK, null, null, bitState.Value.connectionNumber);
if (byteState.Key.Count == 0) return new KeyValuePair<UNPACK_STATUS, byte[]>(UNPACK_STATUS.ERROR, null);
List<byte> packet = byteState.Key;
//crc test
byte[] crc = packet.Skip(len + 1).Take(2).ToArray();
ushort crcShort = (ushort)((crc[0] << 8) | crc[1]);
//skip start bytes, crc, and end bytes
return new KeyValuePair<UNPACK_STATUS, byte[]>(UNPACK_STATUS.GOOD_MESSAGE, packet.ToArray());
}
static KeyValuePair<List<byte>, StateObject> ReadWrite(PROCESS_STATE ps, Socket handler, IAsyncResult ar, long unpackConnectionNumber)
{
KeyValuePair<List<byte>, StateObject> byteState = new KeyValuePair<List<byte>, StateObject>(); ;
StateObject stateObject = null;
int bytesRead = -1;
int workingBufferLen = 0;
List<byte> working_buffer = null;
byte[] buffer = null;
Object thisLock1 = new Object();
lock (thisLock1)
{
switch (ps)
{
case PROCESS_STATE.ACCEPT:
acceptDone.WaitOne();
acceptDone.Reset();
stateObject = new StateObject();
stateObject.buffer = new byte[BUFFER_SIZE];
connectionDict.Add(connectionNumber, new KeyValuePair<List<byte>, StateObject>(new List<byte>(), stateObject));
stateObject.connectionNumber = connectionNumber++;
stateObject.workSocket = handler;
byteState = new KeyValuePair<List<byte>, StateObject>(null, stateObject);
acceptDone.Set();
break;
case PROCESS_STATE.READ:
//catch when client disconnects
//wait if accept is being called
//acceptDone.WaitOne();
try
{
stateObject = ar.AsyncState as StateObject;
// Read data from the client socket.
bytesRead = stateObject.workSocket.EndReceive(ar);
if (bytesRead > 0)
{
byteState = connectionDict[stateObject.connectionNumber];
buffer = new byte[bytesRead];
Array.Copy(byteState.Value.buffer, buffer, bytesRead);
byteState.Key.AddRange(buffer);
}
//only put one instance of connection number into fifo
if (!fifo.Contains(byteState.Value.connectionNumber))
{
fifo.Add(byteState.Value.connectionNumber);
}
}
catch (Exception ex)
{
//will get here if client disconnects
fifo.RemoveAll(x => x == byteState.Value.connectionNumber);
connectionDict.Remove(byteState.Value.connectionNumber);
byteState = new KeyValuePair<List<byte>, StateObject>(new List<byte>(), null);
}
break;
case PROCESS_STATE.PROCESS:
if (fifo.Count > 0)
{
//get message from working buffer
//unpack will later delete message
//remove connection number from fifo
// the list in the key in known as the working buffer
byteState = new KeyValuePair<List<byte>, StateObject>(connectionDict[fifo[0]].Key, connectionDict[fifo[0]].Value);
fifo.RemoveAt(0);
//put a valid value in fifoCount so -1 below can be detected.
byteState.Value.fifoCount = fifo.Count;
}
else
{
//getting here is normal when there is no more work to be performed
//set fifocount to zero so rest of code know fifo was empty so code waits for next receive message
byteState = new KeyValuePair<List<byte>, StateObject>(null, new StateObject() { fifoCount = -1 });
}
break;
case PROCESS_STATE.UNPACK:
try
{
working_buffer = connectionDict[unpackConnectionNumber].Key;
workingBufferLen = working_buffer[2];
if ((working_buffer[0] != 0x78) && (working_buffer[1] != 0x78) && (working_buffer[workingBufferLen + 3] != 0x0D) && (working_buffer[workingBufferLen + 4] != 0x0A))
{
working_buffer.Clear();
return new KeyValuePair<List<byte>, StateObject>(new List<byte>(), null);
}
List<byte> packet = working_buffer.GetRange(0, workingBufferLen + 5);
working_buffer.RemoveRange(0, workingBufferLen + 5);
byteState = new KeyValuePair<List<byte>, StateObject>(packet, null);
}
catch (Exception ex)
{
int testPoint = 0;
}
break;
}// end switch
}
return byteState;
}
public static void AcceptCallback(IAsyncResult ar)
{
try
{
// Get the socket that handles the client request.
// Retrieve the state object and the handler socket
// from the asynchronous state object.
Socket listener = (Socket)ar.AsyncState;
Socket handler = listener.EndAccept(ar);
// Create the state object.
StateObject state = ReadWrite(PROCESS_STATE.ACCEPT, handler, ar, -1).Value;
handler.BeginReceive(state.buffer, 0, BUFFER_SIZE, 0,
new AsyncCallback(ReadCallback), state);
}
catch (Exception ex)
{
int myerror = -1;
}
}
public static void ReadCallback(IAsyncResult ar)
{
try
{
StateObject state = ar.AsyncState as StateObject;
Socket handler = state.workSocket;
// Read data from the client socket.
KeyValuePair<List<byte>, StateObject> byteState = ReadWrite(PROCESS_STATE.READ, handler, ar, -1);
if (byteState.Value != null)
{
allDone.Set();
handler.BeginReceive(state.buffer, 0, BUFFER_SIZE, 0,
new AsyncCallback(ReadCallback), state);
}
else
{
int testPoint = 0;
}
}
catch (Exception ex)
{
int myerror = -1;
}
// Signal the main thread to continue.
allDone.Set();
}
}
}

Socket Error 10054 : Error Handling Issue

Eveyone.
How to resolve the Error code 10054 ? There are some description about this error. Here is my full source code for communication. I want to know whether my code is ok or not.
WSAECONNRESET10054 Connection reset by peer. An existing connection
was forcibly closed by the remote host. This normally results if the
peer application on the remote host is suddenly stopped, the host is
rebooted, the host or remote network interface is disabled, or the
remote host uses a hard close (see setsockopt for more information on
the SO_LINGER option on the remote socket). This error may also result
if a connection was broken due to keep-alive activity detecting a
failure while one or more operations are in progress. Operations that
were in progress fail with WSAENETRESET. Subsequent operations fail
with WSAECONNRESET.
Full Source Code
using System;
using System.Net;
using System.Net.Sockets;
using System.Reflection;
using System.Threading;
using LogManager;
namespace CoreUnitPlatform
{
public class SocketCommCoreUnit
{
#region property
private volatile bool _shouldStop;
private LogWriter log = LogWriter.Instance;
private bool m_bSocketConnected = false;
private Socket m_clientSocket = null;
private SocketCommType m_connectedSockType;
private EventHandlerDataReceived m_evtHandlerDataReceived;
private EventHandlerSocketConnected m_evtHandlerSocketConnected;
private EventHandlerSocketConnectedFailed m_evtHandlerSocketConnectedFailed;
private EventHandlerSocketDisconnected m_evtHandlerSocketDisconnected;
private IPAddress m_IPAddress;
private IPEndPoint m_IPEndPoint;
private int m_portNo;
private Socket m_serverSocket = null;
private Thread m_threadConnectSocket = null;
private string Name = string.Empty;
#endregion
#region constructor
public SocketCommCoreUnit()
{
this.Name = "SocketCommCoreUnit";
Instance();
}
#endregion
#region delegatge
public delegate void EventHandlerDataReceived(string msg);
public delegate void EventHandlerSocketConnected();
public delegate void EventHandlerSocketConnectedFailed();
public delegate void EventHandlerSocketDisconnected();
public enum SocketCommType { SERVER, CLIENT };
public bool SocketConnected
{
get { lock (this) { return m_bSocketConnected; } }
set { lock (this) { m_bSocketConnected = value; } }
}
#endregion
#region public
public void ConnectSocketProc()
{
while (!_shouldStop)
{
try
{
if (SocketConnected == false)
{
if (m_connectedSockType == SocketCommType.SERVER)
{
m_clientSocket = m_serverSocket.Accept(); // If a client is connected, wait for data from client
m_evtHandlerSocketConnected();
SocketConnected = true;
}
else
{
m_clientSocket.Connect(m_IPAddress, m_portNo);
if (m_clientSocket.Connected == true)
{
m_evtHandlerSocketConnected();
SocketConnected = true;
}
}
}
else
{
try
{
byte[] buffer = new byte[1024];
int readBytes = this.m_clientSocket.Receive(buffer);
if (readBytes == 0)
{
this.reConnect();
}
else
{
string received = System.Text.Encoding.ASCII.GetString(buffer);
m_evtHandlerDataReceived(received);
}
}
catch (SocketException sex)
{
if (sex.NativeErrorCode.Equals(10054))
{
log.AddErrorLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Error Occured [{0}]: MESASGE[{1}]\r\nSOURCE[{2}]\r\nTRACE[{3}]", sex.NativeErrorCode, sex.Message, sex.Source, sex.StackTrace));
this.reConnect();
}
}
}
}
catch
{
m_evtHandlerSocketConnectedFailed();
}
Thread.Sleep(100);
}
}
public void Initialize(string IP, int port, SocketCommType sockType, EventHandlerDataReceived evtHandlerDataReceived, EventHandlerSocketConnected evtHandlerDataConnected, EventHandlerSocketDisconnected evtHandlerSocketDisconnected, EventHandlerSocketConnectedFailed evtHandlerSocketConnectedFailed)
{
m_connectedSockType = sockType;
m_evtHandlerDataReceived = evtHandlerDataReceived;
m_evtHandlerSocketDisconnected = evtHandlerSocketDisconnected;
m_evtHandlerSocketConnected = evtHandlerDataConnected;
m_evtHandlerSocketConnectedFailed = evtHandlerSocketConnectedFailed;
m_portNo = port;
m_IPAddress = IPAddress.Parse(IP);
m_IPEndPoint = new IPEndPoint(m_IPAddress, m_portNo);
if (sockType == SocketCommType.SERVER)
{
OpenServer();
}
else
{
OpenClient();
}
}
public void Instance()
{
}
public void OpenClient()
{
try
{
#if _NO_USE_SOCKET
#else
RunClientSocket();
#endif
}
catch (System.Exception ex)
{
log.AddErrorLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Error Occured: MESASGE[{0}]\r\nSOURCE[{1}]\r\nTRACE[{2}]", ex.Message, ex.Source, ex.StackTrace));
}
}
public void OpenServer()
{
try
{
#if _NO_USE_SOCKET
#else
RunServerSocket();
#endif
}
catch (System.Exception ex)
{
log.AddErrorLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Error Occured: MESASGE[{0}]\r\nSOURCE[{1}]\r\nTRACE[{2}]", ex.Message, ex.Source, ex.StackTrace));
}
}
public void Release()
{
try
{
if (this.m_clientSocket != null && this.m_clientSocket.Connected)
{
SocketConnected = false;
m_evtHandlerSocketDisconnected();
this.m_clientSocket.Shutdown(SocketShutdown.Both);
this.m_clientSocket.Close();
}
if (m_serverSocket != null)
{
m_serverSocket.Close();
}
if ((m_threadConnectSocket != null) && (m_threadConnectSocket.IsAlive == true))
{
Thread.Sleep(1);
RequestStop();
SocketConnected = false;
m_threadConnectSocket.Abort();
m_threadConnectSocket.Join();
}
}
catch (System.Exception ex)
{
log.AddErrorLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Error Occured: MESASGE[{0}]\r\nSOURCE[{1}]\r\nTRACE[{2}]", ex.Message, ex.Source, ex.StackTrace));
}
}
public void RequestStop()
{
_shouldStop = true;
}
public void RunClientSocket()
{
m_clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
ConfigureTcpSocket(m_clientSocket, SocketCommType.CLIENT);
m_threadConnectSocket = new Thread(new ThreadStart(ConnectSocketProc));
m_threadConnectSocket.Start();
}
public void RunServerSocket()
{
m_serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
m_serverSocket.Bind(m_IPEndPoint);
m_serverSocket.Blocking = true; // The server socket is working in blocking mode
ConfigureTcpSocket(m_serverSocket, SocketCommType.SERVER);
m_serverSocket.Listen(1);
m_threadConnectSocket = new Thread(new ThreadStart(ConnectSocketProc));
m_threadConnectSocket.Start();
}
public void Send(byte[] msg)
{
#if _NO_USE_SOCKET
#else
if (SocketConnected == false)
{
throw new Exception("SOCKET_NOT_CONNECT_BEFORE_SEND_DATA;");
}
try
{
m_clientSocket.Send(msg);
}
catch (System.Exception ex)
{
SocketConnected = false;
m_evtHandlerSocketDisconnected();
log.AddErrorLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Error Occured: MESASGE[{0}]\r\nSOURCE[{1}]\r\nTRACE[{2}]", ex.Message, ex.Source, ex.StackTrace));
}
#endif
}
#endregion
#region private
private void ConfigureTcpSocket(Socket tcpSocket, SocketCommType socketCommType)
{
//// Don't allow another socket to bind to this port.
//tcpSocket.ExclusiveAddressUse = true;
//// The socket will linger for 10 seconds after
//// Socket.Close is called.
//tcpSocket.LingerState = new LingerOption(true, 10);
// Disable the Nagle Algorithm for this tcp socket.
tcpSocket.NoDelay = true;
//if (socketCommType == SocketCommType.CLIENT)
//{
// tcpSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.DontLinger, false);
// tcpSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
// //tcpSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 3000);
// //tcpSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendTimeout, 3000);
// // Set the receive buffer size to 8k
// tcpSocket.ReceiveBufferSize = 2048;
// // Set the send buffer size to 8k.
// tcpSocket.SendBufferSize = 2048;
//}
//// Set the receive buffer size to 8k
//tcpSocket.ReceiveBufferSize = 1024;
// Set the timeout for synchronous receive methods to
// 1 second (1000 milliseconds.)
//tcpSocket.ReceiveTimeout = 1000;
//// Set the send buffer size to 8k.
//tcpSocket.SendBufferSize = 1024;
// Set the timeout for synchronous send methods
// to 1 second (1000 milliseconds.)
//tcpSocket.SendTimeout = 1000;
//// Set the Time To Live (TTL) to 42 router hops.
//tcpSocket.Ttl = 42;
}
private void ConfigureTcpSocket(Socket tcpSocket)
{
//// Don't allow another socket to bind to this port.
//tcpSocket.ExclusiveAddressUse = true;
//// The socket will linger for 10 seconds after
//// Socket.Close is called.
//tcpSocket.LingerState = new LingerOption(true, 10);
// Disable the Nagle Algorithm for this tcp socket.
tcpSocket.NoDelay = true;
//// Set the receive buffer size to 8k
//tcpSocket.ReceiveBufferSize = 8192;
// Set the timeout for synchronous receive methods to
// 1 second (1000 milliseconds.)
//tcpSocket.ReceiveTimeout = 1000;
//// Set the send buffer size to 8k.
//tcpSocket.SendBufferSize = 8192;
// Set the timeout for synchronous send methods
// to 1 second (1000 milliseconds.)
//tcpSocket.SendTimeout = 1000;
//// Set the Time To Live (TTL) to 42 router hops.
//tcpSocket.Ttl = 42;
}
private void reConnect()
{
try
{
SocketConnected = false;
m_evtHandlerSocketDisconnected();
m_clientSocket.Disconnect(true);
log.AddSystemLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Try Re-Connection..."));
if (m_connectedSockType == SocketCommType.SERVER)
{
}
else
{
m_clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
}
}
catch (System.Exception exc)
{
log.AddErrorLog(this.Name, MethodBase.GetCurrentMethod().Name, string.Format("Error Occured: MESASGE[{0}]\r\nSOURCE[{1}]\r\nTRACE[{2}]", exc.Message, exc.Source, exc.StackTrace));
}
}
#endregion
}
}

I made a (IMOHO) nice post about async sockets here, It has some pseudo code about server/client sockets.
Article: Unable to read data correctly from .Net socket in C#
I think the code of Asynchronous example is great.

Handling exceptions in Socket programming

public partial class Form1 : Form
{
private void button1_Click(object sender, EventArgs e)
{
String text = textBox1.Text;
UdpClient udpc = new UdpClient(text,8899);
IPEndPoint ep = null;
while (true)
{
MessageBox.Show("Name: ");
string name = "Connected";
if (name == "") break;
byte[] sdata = Encoding.ASCII.GetBytes(name);
udpc.Send(sdata, sdata.Length);
if (udpc.Receive(ref ep)==null)
{
MessageBox.Show("Host not found");
}
else
{
byte[] rdata = udpc.Receive(ref ep);
string job = Encoding.ASCII.GetString(rdata);
MessageBox.Show(job);
}
}
}
I'm getting an error message when my remote machine is not connected . with this code im getting the errror.
if (udpc.Receive(ref ep)==null)
error message is socket exception was unhanded ( An existing connection was forcibly closed by the remote host)

Wrap the code in a
try
{
}
catch(SocketException se)
{
}
catch(Exception ex)
{
}
And start here for documentation on SocketException
http://msdn.microsoft.com/en-us/library/system.net.sockets.socketexception.aspx

If the exception is unhandled, so handle the exception:
while (true)
{
MessageBox.Show("Name: ");
string name = "Connected";
if (name == "") break;
byte[] sdata = Encoding.ASCII.GetBytes(name);
try{
udpc.Send(sdata, sdata.Length);
byte[] rdata = udpc.Receive(ref ep);
string job = Encoding.ASCII.GetString(rdata);
MessageBox.Show(job);
}
catch(Exception ex)
{
MessaageBox.show(ex.toString());
}
}
The try...catch block is always recommended when the program accesses external resources (dbs, queues, file systems, http connections, udp sockets etc.)

You can wrap your infinite loop in a try catch block.
try
{
while(true)
{
//your code
}
}
catch(Exception exception)
{
//show exception.Message;
}
finally{ //clean up}
Look at how it is done.

Need help with a C# Asynchronous Socket Program that has multiple sends

So, I have a board game that uses Asynchronous socket to operate over LAN. The thing is, I have little to no understanding of Asynchronous socket programming, or of threads, but I do my best to try.
I based my program off a chat program, so I use that part to send multiple strings.
So, here's part of the code for the Client:
private void Connect(IAsyncResult iar)
{
try
{
Socket client_conn = (Socket)iar.AsyncState;
client_conn.EndConnect(iar);
g_bmsg = new byte[1024];
check = true;
string szData = "#Player " + lblName.Text + " connected.";
sendingFunction(szData);
g_client_conn.BeginReceive(g_bmsg, 0, g_bmsg.Length, SocketFlags.None, new AsyncCallback(Receive), g_client_conn);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString(), "GG");
}
}
private void Send(IAsyncResult iar)
{
Socket client_conn = (Socket)iar.AsyncState;
client_conn.EndSend(iar);
}
private void Receive(IAsyncResult iar)
{
if (g_bmsg.Length != 0)
{
SetLabelText(Encoding.ASCII.GetString(g_bmsg, 0, g_bmsg.Length));
check = false;
}
}
private void SetLabelText(string txt)
{
if (lblBuffer.InvokeRequired)
lblBuffer.Invoke(new MethodInvoker(delegate { SetLabelText(txt); }));
else
{
lblBuffer.Text = txt;
}
if (lblBuffer.Text.StartsWith("#"))
{
lblStatmsg.Text = lblBuffer.Text.Replace("#", "");
}
if (lblBuffer.Text.StartsWith("$"))
{
lblStatmsg.Text = "Server Settings Received.";
lblBuffer.Text = lblBuffer.Text.Replace("$", "");
option_Postn = int.Parse(lblBuffer.Text.Substring(0, 1));
option_First = int.Parse(lblBuffer.Text.Substring(2, 1));
}
if (lblBuffer.Text.StartsWith("#"))
{
MessageBox.Show(lblBuffer.Text);
}
}
And here's part of the code for the Server:
private void Accept(IAsyncResult iar)
{
Socket server_conn = (Socket)iar.AsyncState;
g_server_conn = server_conn.EndAccept(iar);
g_bmsg = new byte[1024];
check = true;
g_server_conn.BeginReceive(g_bmsg, 0, g_bmsg.Length, SocketFlags.None, new AsyncCallback(Recieve), g_server_conn);
}
private void Send(IAsyncResult iar)
{
Socket server_conn = (Socket)iar.AsyncState;
server_conn.EndSend(iar);
}
private void Recieve(IAsyncResult iar)
{
try
{
Socket server_conn = (Socket)iar.AsyncState;
server_conn.EndReceive(iar);
if (g_bmsg.Length != 0)
{
SetLabelText(Encoding.ASCII.GetString(g_bmsg, 0, g_bmsg.Length));
check = false;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString(), "GG");
}
}
private void SetLabelText(string txt)
{
if (lblBuffer.InvokeRequired)
lblBuffer.Invoke(new MethodInvoker(delegate { SetLabelText(txt); }));
else
{
lblBuffer.Text = txt;
}
if (lblBuffer.Text.StartsWith("#"))
{
lblStatmsg.Text = lblBuffer.Text.Replace("#", "");
}
else if (lblBuffer.Text.StartsWith("#"))
{
MessageBox.Show(lblBuffer.Text);
}
else if (lblBuffer.Text.StartsWith("%"))
{
}
}
Basically, since the game sends more than messages (it can send settings, or game pieces, etc), I ran the sender function everytime I need to send something, and on the other side, the Receiver decodes the string sent based on the first character (# means the string is a setting, for example).
The problem is, after the first time both host and client sent something to one another, they can't seem to send again. No error, no message, no nothing. Just won't send. Is there something wrong with the sendingFunction? Or perhaps the delegate something? I don't know. Some advice would be appreciated, guys. And thanks in advance.

You're never calling BeginReceive again. The typical practice in async socket programming is to process the received data, then call BeginReceive again so that you can then process the next bit of data that comes in.