You can always use Flash to take advantage of a PHP/MySQL
backbone to achieve a desired 'networking' effect. [use the
function getURL("target.php?asdf=asdf", "POST") to send and receive
data]
I think there's something called a Flash Media Server or something
like that for those who wish to create a temporary server for Flash
apps to connect to.
Also, for P2P, you can always try the .NET languages (eg C#, VB).
There are some libraries for networking functions.
Lastly, there's the JSP library for Java but not recommended
because Java is a bit slow in running, even slower than fellow
interpreted codes like C#.