Trouble communicating between Client/Server C++

Question

I have a client(c++) / server(c) program and currently I'm having difficulty communicating between them (I can't see what the client says on the server and vice versa). Also I am trying have this project multi-threaded, or at least accept multiple connections from clients. All help is greatly appreciated here is the code pertaining to chatting, you can view it in its entirety here

client:

    recv(sockfd , server_reply , 2000 , 0);

    puts("Enter message :"); // asking for password
    scanf("%s" , message);
    send(sockfd , message , strlen(message) , 0);

    recv(sockfd, server_reply, 2000, 0);
    //Receive a reply from the server
    if( recv(sockfd , server_reply , 2000 , 0) < 0)
    {
        puts("recv failed");
    }

while( (read_size = recv(nsockfd , server_reply , 4000 , 0)) != 0)
  {

    puts("Enter message :"); // asking for password
    scanf("%s" , message);
    send(sockfd , message , strlen(message) , 0);

    recv(sockfd, server_reply, 2000, 0);


  }

Server

      char client_address[90];
    sprintf(client_address, "Welcome %s", inet_ntoa(addr_remote.sin_addr));

    char welc_msg[90] = "Welcome %s";
    char friend_msg[50] = "Hello little friend \n";
    char username[30] = "Enter user:";
    char pass[30] = "Enter pass: ";

    write(nsockfd , client_address , strlen(client_address)); // attempting to send client "Hello, (their ip address)"
    read_size = recv(nsockfd , client_message , 4000 , 0);

    read_size = recv(nsockfd , client_message , 4000 , 0);
printf( "%s", client_message);
printf( "\n");



//Receive a message from client
while( 1 )  //    while( (read_size = recv(nsockfd , client_message , 4000 , 0)) != 0)
{
    //clearing buffer
    memset(client_message, 0, sizeof(client_message));

    //taking received message and printing it
    read_size = recv(nsockfd , client_message , 4000 , 0);
        printf( "%s", client_message);
        printf( "\n");

    //Send the message back to client
   // write(nsockfd , server_message , strlen(server_message));


    if (strcmp(client_message , "Hello")) // condition for project
    {
        write(nsockfd, friend_msg, strlen(friend_msg));
    }

}

Answer 1

Try this code: Server.c

while (1) {
    //---- ACCEPT connection ------------------------------------
    sa = accept(s, 0, 0);                  // block for connection request  
    if (sa < 0) {
        printf("accept error %ld ", WSAGetLastError() ); 
        WSACleanup();
        return false;
    }
    else {
        printf("connection accepted");
    }
/*  gets(buf);
    bytesSent = send( s, buf, 10, 0 ); 
    printf( "Bytes Sent: %ld \n", bytesSent );*/

    //------------------------------------------------------------
    // Socket is now set up and bound. Wait for connection and process it. 

    //---- RECV bytes --------------------------------------------
    bytesRecv = recv( sa, recvbuf, 10, 0 );
    err = WSAGetLastError( );// 10057 = A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) 
    if ( bytesRecv == 0 || bytesRecv == WSAECONNRESET ) {
      printf( "Connection Closed.\n");
      WSACleanup();
    }
    printf( "\nBytes Recv from Client: %s \n ", recvbuf );

    //-------------------------------------------------------------
//  if(bytesRecv != 0 || bytesRecv != WSAECONNRESET){

    bytesSent = send( sa, buf, 10, 0 ); 
    if(bytesSent == -1)
    {
        //break;
        puts("Error\n");
    }
    else
    {
    printf( "Bytes Sent: %ld \n", bytesSent );
    Sleep(1000);
    }
    closesocket( sa );
    }

Client.c

while(1) {
    //--- INITIALIZATION -----------------------------------
    wVersionRequested = MAKEWORD( 1, 1 );
    err = WSAStartup( wVersionRequested, &wsaData );

    if ( err != 0 ) {
        printf("WSAStartup error %ld", WSAGetLastError() );
        WSACleanup();
        return false;
    }
    //------------------------------------------------------

    //---- Build address structure to bind to socket.--------  
    target.sin_family = AF_INET; // address family Internet
    target.sin_port = htons (SERVER_PORT); //Port to connect on
    target.sin_addr.s_addr = inet_addr (IPAddress); //Target IP
    //--------------------------------------------------------


    // ---- create SOCKET--------------------------------------
    s = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP); //Create socket
    if (s == INVALID_SOCKET)
    {
        printf("socket error %ld" , WSAGetLastError() );
        WSACleanup();
        return false; //Couldn't create the socket
    }  
    //---------------------------------------------------------


    //---- try CONNECT -----------------------------------------
    if (connect(s, (SOCKADDR *)&target, sizeof(target)) == SOCKET_ERROR)
    {
        printf("connect error %ld", WSAGetLastError() );
        WSACleanup();
        return false; //Couldn't connect
    }
    //-----------------------------------------------------------

    //---- SEND bytes -------------------------------------------

    bytesSent = send( s, buf, 10, 0 );
    printf( "Bytes Sent: %ld \n", bytesSent );
    Sleep(1000);


    if((bytesRecv = recv( s, recvbuf, 10, 0 )) == SOCKET_ERROR)
    {
        puts("Socket Error");
        err = WSAGetLastError( );// 10057 = A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) 
    }
    else
    {
    if ( bytesRecv == 0 || bytesRecv == WSAECONNRESET ) {
      printf( "Connection Closed.\n");
      WSACleanup();
    }
    printf( "\nBytes Recv from Server: %s \n ", recvbuf );
    //closesocket( sa );
    }
    //------------------------------------------------------------
    closesocket( s );
    WSACleanup();
    }

The above code strictly for Windows.

Answer 2

When you call the system functions, always check for errors! Where relevant, also check for partial writes / receives. For example, when you have this line:

send(sockfd , message , strlen(message) , 0);

You should have something like this (untested, so think it through yourself):

(Edit: removed unnecessary resend loop to simplify code. See edit history if you want to see it...)

int msglen = strlen(message);
fprintf(stderr, "debug: about to send %d bytes", msglen);

int sent = send(sockfd , message , msglen , 0);

if (sent == -1) { // for each function, read docs for error result
    perror("send message");
    // do some error handling
} else if (sent < msglen) {
    fprintf(stderr, "debug: partial send %d/%d\n", sent, msglen);
    // do some disconnect handling
}

Once you have proper error reporing, and if you can't solve your problem with that, then update the question with this debug/error information.