about Winsock send() and recv()

Hello!

I'm very new on C and Winsock programming (i did some VB with winsock
control).
I've started with a little app. It works pretty well using an ECHO
server: i send a message, and i receive the same. Cool.
But, when i connect with a SMTP, POP or any other service, i receive a
first message, and then it hangs up.

My code:

/******* part: LOOP */
        int con = connect(recvskt, (SOCKADDR*) &RetSocket,
sizeof(RetSocket));
        if(con != SOCKET_ERROR){
            do{
                sendm(recvskt);
                if(recvm(recvskt) == 0){printf("Block.");}
            }while(rcv_b != SOCKET_ERROR);
        }else{exit;}

/********** end */

And the send and receive functions (which are properly declared):

/********* functions */

int sendm(int socket){
    FD_SET writeable;
    FD_ZERO(&writeable);
    FD_SET(socket, &writeable);
    if(select(socket, 0, &writeable, 0, 0) != SOCKET_ERROR){
        scanf("%s\r\n", request);
        snd_b = strlen(request);
        snd_b = send(socket, (char *)request, (snd_b + 1), 0);
        return snd_b;
    }else{return(0);}
}

int recvm(int socket){
    FD_SET readable;
    FD_ZERO(&readable);
    FD_SET(socket, &readable);
    if(select(socket, &readable, 0, 0, 0) != SOCKET_ERROR){
        rcv_b=recv(socket, (char *)buffer, sizeof(buffer), 0);
        buffer[rcv_b] = NULL;
        strcat(temp, buffer);
        printf("%s\r\n", buffer);
        return rcv_b;
    }else{return(0);}
}

/*********** end */+

Please help. I do not understand why with an ECHO server things works
and not the same with other services. I just want to write a simple
"telnet" or tcp chat app.

Thanks
Nicolas