C# async socket for multi-client

Question

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace sockasyncsrv
{
    class Program
    {
        static void Main(string[] args)
        {
            RunAsyncSocketServer().Wait();
        }

        static async Task RunAsyncSocketServer()
        { 
            int MAX_SIZE = 1024; 

            Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);


            IPEndPoint ep = new IPEndPoint(IPAddress.Any, 7000);
            sock.Bind(ep);

            sock.Listen(100);

            while (true)
            {
                Socket clientSock = await Task.Factory.FromAsync(sock.BeginAccept, sock.EndAccept, null);

                var buff = new byte[MAX_SIZE];

                int nCount = await Task.Factory.FromAsync<int>(
                           clientSock.BeginReceive(buff, 0, buff.Length, SocketFlags.None, null, clientSock),
                           clientSock.EndReceive);

                if (nCount > 0)
                {
                    string msg = Encoding.ASCII.GetString(buff, 0, nCount);
                    Console.WriteLine(msg);

                    await Task.Factory.FromAsync(
                            clientSock.BeginSend(buff, 0, buff.Length, SocketFlags.None, null, clientSock),
                            clientSock.EndSend);
                }

                clientSock.Close();
            }
        }
    }
}

After a client connect my server, then I want to continue to receive message from the connected client. So I used 'while(true)' above 'if(nCount>0)', then it is impossible to accept another clients. How to get multi-client?

Short answer: Threading. You need to spawn a thread for each client and keep the ServerSocket listening and accepting connections while the spawned threads handle communication with each Client Socket concurrently. — Fildor
– Fildor, Commented Jan 24, 2018 at 9:13

Chris Fraser · Accepted Answer · 2018-01-24 09:29:39Z

2

You need multiple sockets for multiple connections. A Soket is designet to handle one connection. You can Create a new Socket that waits for a connectino once the first one has a connection.(wen the thread enters the while (true) loop)

You could also have multiple sockets listen at the same time. Maby on a different port? Soemthing like this.

    static async Task RunAsyncSocketServer(int port)
    {
        int MAX_SIZE = 1024;

        Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);


        IPEndPoint ep = new IPEndPoint(IPAddress.Any, port);

edited Jan 24, 2018 at 9:29

answered Jan 24, 2018 at 9:17

Chris Fraser

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