Network Programming

• The SOCKETS library of subroutines has been developed to provide a simple programming interface to networking services.
• A typical program fragment (in PERL) may look like this:

             $proto = getprotobyname('tcp');   % determine protocol for IP header
             socket(Socket_Handle, PF_INET, SOCK_STREAM, $proto); % create a socket
             $port = getservbyname('smtp');    % determine destination port
             $sin = sockaddr_in(7,inet_aton("localhost")); % form address info
             connect(Socket_Handle,$sin);      % Initiate TCP connection
  

• Now one can read and write to the Socket_Handle as if it were a regular file.
• All details of packetizing, appending headers, etc. are performed by networking software in the operating system.