Re: about Winsock send() and recv()
"nfiglesias@gmail.com" <nfiglesias@gmail.com> wrote:
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.
...
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);}
}
The problem is your use of the dangerous "scanf" function. Because of the
way you have called this, the "request" variable will not have a CR or LF
at the end -- scanf will remove it. TCP services like SMTP and POP always
expect lines to end with a end-of-line sequence (usually \r\n, although
every server I've encountered accepts a lone \n).
So, it's just like you telnetted into your SMTP server, and typed
HELO gmail.com
without pressing return at the end. You'd hang.
Use "fgets" instead of "scanf".
--
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.