Check SMTP server on startup

Hey,

my program requires a working SMTP server. So i do a first check on startup.

This is the test:

Code:

bool Mail::checkSMTP(){
	char echoBuffer[64];
	int bytesRcvd = 0;
	int create_socket;
	struct sockaddr_in address;
	char* answerCode;
	if((create_socket = socket(AF_INET, SOCK_STREAM,0)) > 0){
		// Socket created.  
		address.sin_family = AF_INET;
		address.sin_port = htons(smtpport);
		address.sin_addr.s_addr = resolveName(hostname);
		if(connect(create_socket,(struct sockaddr *) &address, sizeof(address)) == 0){
			// Connected to server. - Get answer. 
			if((bytesRcvd = recv(create_socket, echoBuffer, 63,0)) <= 0) return 0;
			answerCode = strtok(echoBuffer, " ");
			if(strcmp(answerCode,"220") == 0){
				close(create_socket);
				return 1;
			}else{
				return 0;
			}
		}else{
			// Could not connect to server.  
			close(create_socket);
			return 0;
		}
	}
	return 0;
}

The Problem: There is no timeout! When there is a firewall or a HTTP service behind the port the startup just stops because i get no answer.

What would be the best way to solve this problem?

Thank you!

Use ethereal to observe what a real email client does in that circumstance, and compare the traffic with that produced by your program.

Originally Posted by Salem

Use ethereal to observe what a real email client does in that circumstance, and compare the traffic with that produced by your program.

alpine does a DNS request and then starts to communicate with the SMTP server like i do.

So if you're producing the same message sequence, why doesn't it work?

Originally Posted by Salem

So if you're producing the same message sequence, why doesn't it work?

I dont know.

I just configured alpine to connect to my SMTP server on port 80. It uses a timeout. After about 1 minute i get "Connection timed out"

AFAIK, 80 is for HTTP. And SMTP uses 25, according to wikipedia.

And make sure your firewall isn't blocking it.

Originally Posted by robwhit

AFAIK, 80 is for HTTP. And SMTP uses 25, according to wikipedia.

And make sure your firewall isn't blocking it.

Well... Ehm... Yes. Read my first post again

I would suggest you compare the message sequences again.

Originally Posted by crisis

Well... Ehm... Yes. Read my first post again

Maybe the firewall is blocking the program on a per-program basis? IDK which end you are having the firewall on, the client side or the server side.

Originally Posted by robwhit

Maybe the firewall is blocking the program on a per-program basis? IDK which end you are having the firewall on, the client side or the server side.

My problem is not that the connection is blocked. I just don't want the program to stop when a connection is blocked. This usually does not happen - But what if it does?

Oh I see.

You could use threads or asynchronous sockets.

To simply get a timeout while waiting for an SMTP or ESMTP, use select(). It will indicate when there is data available on a socket, and it has a timeout parameter.

Use non-blocking sockets and a wait loop. Other than that, the ode you posted shoudl work fine, Your timeout value may just be very long.

Thank you all! I will see what way fits the best for me.