Hi,

To test the functionality of SO_ERROR i wrote a sample code where in connect() throws Connection refused error as server is not running and client tries to establish connection. but getsockopt on this fd returns 0 in error parameter in below function call.

getsockopt(Sockfd, SOL_SOCKET, SO_ERROR, &error, &len);
cout << error << endl; displays 0
I tried this on both Linux and Windows.
Under what scenario will this option returns error value. Please let me know so that i can write the sample code to understand the functionality of SO_ERROR.

Thanks....

Moved: This thread is more suitable in Programming and has been moved accordingly to help your thread/question get the exposure it deserves.

Sorry, but the traditional way to do this is to read "errno" (Linux) or WSAGetLastError () (Windows) at the time of error (i.e. when your "connect()" fails; presumably returning "-1").

This is true for all the socket calls ("socket()", "accept()", "setsockopt ()", etc etc).

I suspect the problem here is that, because the "connect()" failed, you don't actually have a socket and there's nothing for "getsockopt ( SO_ERROR )" to return.

But I'm not sure under what circumstances you can legitimately call "getsockopt ( SO_ERROR )", or how portable this approach is. There's really no easy way to adapt a "try/catch" style of programming without writing your own wrapper classes (or using somebody else's OO socket wrappers).

I would definitely encourage you to simply check for (and respond to) errors at the point of call. I would also encourage you to become thoroughly comfortable with "procedural sockets", even if you do ultimately wind up using a higher-level, OO library. Here are two excellent references:

http://beej.us/guide/bgnet/
Stevens, Unix Network Programming (3rd Ed):
http://www.amazon.com/Unix-Network-P...dp/0131411551/

IMHO .. PSM

But I'm not sure under what circumstances you can legitimately call "getsockopt ( SO_ERROR )"

This call is for when using "non-blocking" connect calls (after fcntl(fd, O_NONBLOCK)). In that case, the connect system call returns right away, and actual completion can be probed for using select(). Once completed, you use getsockopt(SO_ERROR) on the handle to check whether completion was successful or not, and, if unsuccessful, which failure condition applies.