Win32 Socket Client


  Socket programming in MFC is usually a bit messy. It’s always clean and convenient to write the socket programs using Win32.

  A big advantage writing these programs in Win32 is, we can follow the same model as in any Unix C++ socket program. Also, with each and every new version of Winsock, we don’t know how many bugs are going to get added to the development frameworks.

Anyway, now let’s get down to business. This article does not try to cover all the minute details of winsock client programming, but for the basics. The relevant steps for creating a synchronous client socket are:

 

 

  1. Create a socket and get the handle
  2. Populate the SOCKADDR_IN structure with the Server IP and Port Number
  3. Connect using the connect function
  4. Send and Recv using the socket
  5. Shutdown and Close when all jobs are done

 

The following sample illustrates the above steps. Only one item missed out here is the usage of recv function.



#include <winsock2.h>
#include <iostream.h>
int gPort = 8780;
void main()
{
       SOCKET lhSocket;
       SOCKADDR_IN lSockAddr;
       WSADATA wsaData;
       int lConnect;
       int lLength;
       char lData[]=”SendData”;
       if(WSAStartup(MAKEWORD(2,0),&wsaData) != 0)
       {
            cout<<”Socket Initialization Error. Program abortedn”;
            return;
        }
       lhSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
       if(lhSocket == INVALID_SOCKET)
       {
            cout<<”Invalid Socket “<<GetLastError()<<”. Program Abortedn”<<endl;
        }
       memset(&lSockAddr,0, sizeof(lSockAddr));
       lSockAddr.sin_family = AF_INET;
       lSockAddr.sin_port = htons(gPort);
       lSockAddr.sin_addr.s_addr = inet_addr(“IPAddress”);
       lConnect = connect(lhSocket,(SOCKADDR *)&lSockAddr,sizeof(SOCKADDR_IN));
       if(lConnect != 0)
       {
             cout<<”Connect Error. Program abortedn”;
             return;
        }
       lLength = send(lhSocket,lData,strlen(lData),0);
       if(lLength < strlen(lData))
       {
            cout<<”Send Error.n”;
       }
       closesocket(lhSocket);
       return;
}


Note:
The socket programs in MFC need the library ws2_32.lib to be referenced before linking. Otherwise the VC++ linker throws errors.