17.16. Writing a Multihomed Server17.16.1. ProblemYou want to write a server that knows that the machine it runs on has multiple IP addresses, and that it should possibly do different things for each address. 17.16.2. SolutionDon't bind your server to a particular address. Instead, bind to INADDR_ANY. Then once you've accept ed a connection, use getsockname on the client socket to find out which address the client connected to: use Socket; socket(SERVER, PF_INET, SOCK_STREAM, getprotobyname('tcp')); setsockopt(SERVER, SOL_SOCKET, SO_REUSEADDR, 1); bind(SERVER, sockaddr_in($server_port, INADDR_ANY)) or die "Binding: $!\n"; # accept loop while (accept(CLIENT, SERVER)) { $my_socket_address = getsockname(CLIENT); ($port, $myaddr) = sockaddr_in($my_socket_address); } 17.16.3. DiscussionWhereas getpeername (as discussed in Recipe 17.7) returns the address of the remote end of the socket, getsockname returns the address of the local end. When we've bound to INADDR_ANY, thus accepting connections on any address the machine has, we need to use getsockname to identify which address the client connected to. If you're using IO::Socket::INET, your code will look like this: $server = IO::Socket::INET->new(LocalPort => $server_port, Type => SOCK_STREAM, Proto => 'tcp', Listen => 10) or die "Can't create server socket: $@\n"; while ($client = $server->accept( )) { $my_socket_address = $client->sockname( ); ($port, $myaddr) = sockaddr_in($my_socket_address); # ... } If you don't specify a local port to IO::Socket::INET->new, your socket will be bound to INADDR_ANY. If you want your server to listen only for a particular virtual host, don't use INADDR_ANY. Instead, bind to a specific host address: use Socket; $port = 4269; # port to bind to $host = "specific.host.com"; # virtual host to listen on socket(Server, PF_INET, SOCK_STREAM, getprotobyname("tcp")) or die "socket: $!"; bind(Server, sockaddr_in($port, inet_aton($host))) or die "bind: $!"; while ($client_address = accept(Client, Server)) { # ... } 17.16.4. See AlsoThe getsockname function in Chapter 29 of Programming Perl and in perlfunc(1); the documentation for the standard Socket and IO::Socket modules; the section on "Sockets" in Chapter 16 of Programming Perl or perlipc(1) Copyright © 2003 O'Reilly & Associates. All rights reserved. |
|