Testing multiplayer client/server with UDP?

Question

I'm using UDP for a game that I am making, but this issue is not nescessarily game-specific. I have noticed that whenever I want to test something locally and I use broadcasting, there's a chance that the UDP client sending some data out is also the same client receiving it again, instead of the other client also connected from the same machine.

How can I test and debug this effectively on one machine, simulating it in used condition on two machines?

score 3 · Accepted Answer · answered Nov 24 '11 at 22:12

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Two options:

Use a different port for each direction of traffic, e.g. client -> server is port 2001, server -> client is port 2002.
Use a virtual machine. You can use VirtualBox or VMWare to set up a virtual OS, complete with network cards.

The latter option will not require you to change your code, but you'll need to copy the server or client application to the VM every time you change the code.

answered Nov 24 '11 at 22:12

Polynomial

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But with UDP, I can't have 2 different ports, can I? – Mathias Lykkegaard Lorenzen Nov 24 '11 at 22:20
Yes, you can have multiple ports. Just use two instances of `UdpClient`. If you're broadcasting, either use multicast on two separate channels, or do as CodeCaster said and place a "to" header in the message. – Polynomial Nov 24 '11 at 22:29
Using a virtual machine is not an option, since I am running a game. It can't graphically run on the VM. – Mathias Lykkegaard Lorenzen Nov 27 '11 at 10:52

score 1 · Answer 2 · answered Nov 24 '11 at 22:21

1

Don't you use some kind of identifier (username or id) to detect who sent the original message?

Check if a received message is sent from the same identifier as the receiver has, and if so, discard the message.

answered Nov 24 '11 at 22:21

CodeCaster

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For some reason though (according to my debugging results), only one of the clients receive the message. The other doesn't. – Mathias Lykkegaard Lorenzen Nov 24 '11 at 22:34
@Mathias weird, it should be [possible](http://stackoverflow.com/questions/1694144/can-two-application-listen-to-the-same-port). – CodeCaster Nov 24 '11 at 22:39
I see. Any ideas on why it may be happening? Reuse address is set to true just fine. – Mathias Lykkegaard Lorenzen Nov 24 '11 at 22:57

Testing multiplayer client/server with UDP?

2 Answers2