Using TCP sockets in Perl Created by M Bateman, A Ruddle & C Allison As part of the TCP View project

Overview TCP socket Client/Server Multithread server Thread pooling server Alternate thread pooling server

TCP Provides Process to process communication –Use tuple of IP address & port Reliable In order Socket is one end-point of a two way connection link

TCP Socket Operations

TCP in Perl Implemented in Socket package Provides abstractions over –Socket and connect operations –Bind, listen & accept Remember to close the socket at the end

Daytime server use Socket; $port = 13; $proto = getprotobyname (‘tcp’); socket (SERVER, PF_INET, SOCK_STREAM, $proto); setsockopt (Server, SOL_SOCKET, SO_REUSEADDR, pack (“1”, 1)); bind (SEVER, socket_in ($port, INADDR_ANY)) listen (SERVER, SOMAXCONN); for (; $paddr = accept (CLIENT, SERVER); close CLIENT) { print (CLIENT scalar localtime. “\n”); }

Daytime client use Socket; $port = 13; $remote = $ARGV[0]; $iaddr = inet_aton ($remote); $paddr = sockaddr_in ($port, $iaddr); $proto = getprotobyname (‘tcp’); socket (SOCK, PF_INET, SOCK_STREAM, $proto); connect (SOCK, $paddr); while ($line = ) { print ($line); } Close (SOCK);

Issues Can only deal with one request at once Performance –Have to wait until the guy in front has finished with the server

Multithreading

Issues Performance –Thread creation at client connection –Creating threads takes time Possible deadlock –Due to multithreaded

Issues Possible deadlock Resource thrashing Concurrency errors Thread leakage Request overload Performance –Thread creation still has to be performed in the main loop

Pool Alternative Implementation Create pool as before Create thread which makes sure the pool has n thread waiting On connection take thread from the pool –The above thread makes sure there are always threads in the pool waiting to be used

Summary