how to accept multiple clients with a simple winsock tcp server?

Question

I can't figure out how to accept multiple connections for a simple tcp server using winsock.

I've tried a couple different ways and I can't figure out how to get another connection to work. The first call to accept() seems to be the only one that works. Can someone provide a simple example of how to do this or explain what's going on with listen() and accept() here?

#include <string>
#include <Winsock2.h>

WSADATA WsaData; 
unsigned char packet_in[64];
unsigned short port = 29992;
unsigned int max_packet_size =  sizeof(packet_in);
sockaddr_in xaddress;
SOCKET sock;
SOCKET sock1 = INVALID_SOCKET;
SOCKET sock2 = INVALID_SOCKET;

int main()
{   

    int r = WSAStartup( MAKEWORD(2,2),  &WsaData );
    xaddress.sin_family = AF_INET; 
    xaddress.sin_port =  htons(port);
    DWORD nonBlocking = 1;
    sockaddr_in from; 
    int fromLength = sizeof( from );  
    int count = 0;

    sock = socket( AF_INET,  SOCK_STREAM,  IPPROTO_TCP );   

    r = bind(sock, (const sockaddr*) &xaddress,  sizeof(sockaddr_in));
        if (r != 0) printf("%d\n", WSAGetLastError());

    r = listen(sock, SOMAXCONN);
    if (r == SOCKET_ERROR)
            printf("%d\n",WSAGetLastError());

    ioctlsocket(sock, FIONBIO, &nonBlocking);

    while(true)
    {

        if(count == 0)
        {
            sock1 = accept(sock, NULL, NULL);

        }
        else if (count == 1)
        {
            sock2 = accept(sock, NULL, NULL);

        }

        if(sock1 != INVALID_SOCKET)
            count = 1;
        if(sock2 != INVALID_SOCKET)
            count = 2;
        printf("%i\n",count);


    }
    return 0;
}

Does it get inside your second `if statement -- if (count == 1)`? You should post the output and errors you get after a call to `WSAGetLastError`. — Brandon, Jan 01 '16 at 19:50
Try: `struct sockaddr_storage ss; socklen_t slen = sizeof(ss); SOCKET fd = accept(listener, (struct sockaddr*)&ss, &slen); ioctlsocket(sock, FIONBIO, &nonBlocking);` — Brandon, Jan 01 '16 at 19:59
Possible duplicate of [TCP Winsock: accept multiple connections/clients](http://stackoverflow.com/questions/15185380/tcp-winsock-accept-multiple-connections-clients) — Ilya, Jan 01 '16 at 20:11
Get rid of the non-blocking mode. You don't have anything else to do in the accept thread, or you shouldn't. — user207421, Jan 01 '16 at 23:01

score 0 · Answer 1 · answered Jan 01 '16 at 20:01

I don't know how to network programming on Windows, but it basically looks like on Linux, so this is small example for Linux.

struct sockaddr_in server_addr
socklen_t len = sizeof(server_addr);
...
while(1)
{
   struct sockaddr_in client_addr;
   int client_fd;
   if((client_fd = accept(server_sock, (struct sockaddr*)& client_addr, &len)) < 0)
   {
      cerr<<"accept() error"<<endl;
      continue;
   }
   ...
}

There is full example written in Polish, but you should understand: full example (find //server.c)

Main differences between network programming on Windows and Linux are structures and classes, so it should give you some knowledge: Beej's guide to network programming

score 0 · Answer 2 · answered Jan 02 '16 at 11:21

I think from this simple program, You will get better idea :)

// Multi-Client - Server chat application

    #include"header.h"

    void isr(int n)
    {
    printf("Client is Disconnected ..\n");
    kill(getpid(),9);
    return;
    }

    main()
    {
        int sockfd,nsfd,len,pid,size;
        char buffer[500],buffer1[500];
        struct sockaddr_in server;
    ///////////////////////////////////////////////////////////////////////
        sockfd=socket(AF_INET,SOCK_STREAM,0);
        if(sockfd==0)
        {
        printf("Socket file is not created socket is fail...\n");
        return;
        }
        ////////////////////////////////////////////////////////////////////////
        server.sin_family=AF_INET;
        server.sin_port=htons(9898);
        len = sizeof(server);
      /////////////////////////////////////////////////////////////////////
        bind(sockfd,(struct sockaddr*)&server,len);
        perror("bind");
      /////////////////////////////////////////////////////////////
        listen(sockfd,5);
        perror("listen");
       /////////////////////////////////////////////////////////////////
        bzero(buffer,sizeof(buffer));
        zero(buffer1,sizeof(buffer1));
        //////////////////////////////////////////////////////////////////////
       while(1)
       {
        nsfd=accept(sockfd,(struct sockaddr *)&server,&len);
            if(nsfd<0)
            {   
                perror("accept");
                return;
            }

           if(fork()==0)
            {
                while(1)
                {
                    size=recv(nsfd,buffer,sizeof(buffer),0);

                    if(size==0)
                    {
                    printf("Server is Disconnected...\n");
                    return;
                    }

                printf("Data:%s\n",buffer);
                bzero(buffer,sizeof(buffer));

                }
           }
        else
        {
            printf("Enter the massage:\n");
            signal(17,isr);

              while(1)
              {
                  gets(buffer);
                  send(nsfd,buffer,strlen(buffer)+1,0);
                   bzero(buffer,sizeof(buffer));
             }
        }            
  }
}

how to accept multiple clients with a simple winsock tcp server?

2 Answers2