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:

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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;
}

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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.

Quote:

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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.

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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?

Quote:

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Originally Posted by Salem

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

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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.

Quote:

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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.

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

I would suggest you compare the message sequences again.

Quote:

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Originally Posted by crisis

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

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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.

Quote:

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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.

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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.