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Thread: Port forwarding: games use different UDP ports, than their designated ports!

  1. #1
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    Question Port forwarding: games use different UDP ports, than their designated ports!

    Hello,

    I have a question about Port Forwading, which was confusing me for awhile... You open ports on your router, because these need to be accessed by external IP address: for games to work properly. I open ports on my router for games, which have specified (on their websites) exact UDP ports you need to open. Strange is that my games are never using these ports on my localhost. I used Wireshark in past, or netstat. And games receive packets on different ports than those I did open in router! Is this because NAT? Does router have its own ports? And then it maps these ports to computer on LAN? I thought ports are endpoints, behind which are applications on computer. E.g. if I open port 6750, I would expect external IP address to send packets to my IP + port 6750 (when I play game which uses this port)! But my games are never listening on these ports - I open in router. Strange... Can you explain please?

  2. #2
    Administrator Philip's Avatar
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    You only need to open ports for incoming connections, when others are connecting to your PC. Most of the UDP ports games use are outgoing, i.e. your game initiates connections to some gameserver which needs those ports open (destination ports). The games will likely work without you opening any ports, since outgoing traffic is allowed on most ports.

    It is an issue of outgoing "source" ports vs "destination" ports: only destination ports need to be open, and that's usually when you run some type of server.
    Linux is user friendly, it's just picky about its friends...
    Disclaimer: Please use caution when opening messages, my grasp on reality may have shaken loose during transmission (going on rusty memory circuits).
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    Yeah that's what I read, most of the time - it should be fine without opening ports... I read from multiple sources, that it is make your network accessible to computers on the internet. In other words: that you need to open your "incoming ports". But truth is - I didn't find many useful articles, mostly it is snake-oil... So I Am just confused at this point. It is strange, because some games said I have strict NAT and after opening ports, it said: that NAT is open. Also I read on the internet people saying: that opening ports helped!

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    Administrator Philip's Avatar
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    Games are designed to work around closed ports, as most people are behind some type of NAT routers and firewalls. In general, NAT blocks incoming connections on non-standard ports, but it does not block outgoing connections. When you start your game, it opens outgoing connections to a game server, so they're not blocked by NAT. In short, when you initiate the connection, it is allowed through NAT, and then the game server can also communicate through that already established connection.

    Some games may work "better" if you open particular ports, as it allows for more ways for the game server to interact with your PC, but it should not be necessary with most modern games. What if you want to have multiple computers on your LAN game at the same time? Whose local IP are you going to forward those ports to?

  5. #5
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    One IP, I have 1 computer on LAN.

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