Pretty much any network library can handle that(RakNet is nice but you could just use raw sockets as well), its not the low level networking itself that tends to be the bottleneck, its the game specific protocol and server architecture. also, running a simulation for 5000 players(+ npcs, monsters, etc, etc, etc) can be fairly demanding, you might (depending on the gameplay mechanics) have to distribute the simulation over multiple physical servers (a fairly difficult problem to solve, if you don't have a solid grasp on distributed simulation i'd recommend designing around that problem instead)
Anything that can run under linux will be a good thing
actually i need something simpler than racknet, something more native which can work on linux a simple client-server engine/lib would do
Anything that can run under linux will be a good thing
actually i need something simpler than racknet, something more native which can work on linux a simple client-server engine/lib would do
BSD/POSIX sockets work under linux and is as simple and native as it can get(as it is the native socket library for *nix).
Allthough RakNet is pretty much the best reasonably priced(its free for games retailing for less than $30 and grossing less than $100k) networking library out there, and it does work great on Linux, Windows, Mac, iOS, Android and WP8 (if you pay for it you can also get it for Xbox360, PS3 and Vita) so i'd still recommend using it. (You will most likely want things like reliable UDP anyway)
