Question

I have this application that consists of two phases. Queuing phase and chatting Phase.

The chatting uses UDP (a flash-app).

So before the user enters the queue phase I want to check if UDP traffic is possible.

I could do this both in the ASP.NET app (that wraps the flash-app) or in the flash-app.

I’m not sure on how to do this in either of them.

My initial thougth is to connect via UDP to some tiny webservice a server, but is there an easier way of doing it ?

It’s not the computer I’m worried about, it’s the router that I want to check.

Answer 1

Unfortunately, the only way to know for sure if a UDP datagram can be routed from one point to another is to try and see what happens. Send a test datagram to the other side and have that send back a response. If you don’t get a response within a second or two, try again. Repeat a couple of times. If you still get nothing back, then you probably don’t have connectivity at that moment

Testing to a different IP address, or even a different port, won’t really help: you might have connectivity to one location but not another.

Also remember all the caveats about UDP:

• Anything you send could disappear at any time, so verify receipt and be prepared to repeat
• Payloads larger than 1400 bytes are much more likely to disappear (see “IP fragmentation”)
• If you must send more than a few packets, then you must control your data rate: too fast and packets will be dropped, the definition of “too fast” will constantly change.

Making UDP work is a lot of work, so consider if you really need it.