Taken from the original at http://beej.us/guide/bgnet/ ... see end of writeup for Copyright statement.
socket()--Get the File Descriptor!
I guess I can put it off no longer -- I have to talk about the socket() system call. Here's the breakdown:
int socket(int domain, int type, int protocol);
But what are these arguments? First, domain should be set to "AF_INET", just like in the struct sockaddr_in (above.) Next, the type argument tells the kernel what kind of socket this is: SOCK_STREAM or SOCK_DGRAM. Finally, just set protocol to "0". (Notes: there are many more domains than I've listed. There are many more types than I've listed. See the socket() man page. Also, there's a "better" way to get the protocol. See the getprotobyname() man page.)
socket() simply returns to you a socket descriptor that you can use in later system calls, or -1 on error. The global variable errno is set to the error's value (see the perror() man page.)
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