Why my UDP messages were blocked?

I used two DatagramSockets in my server part.One is to listen client's login,and write down his InetAddress and port,the other is to send messages to the InetAddress and port .But if the client is behind a proxy server ,the messages will be blocked.why?
[262 byte] By [fool_leavea] at [2007-9-29 18:51:02]
# 1

Most routers/firewalls will not route UDP packets. U have a case where U need to talk to yar MIS guy/fellow to make it happen. Its a simple property-based on the hardware.

Also, the "ttl" on the packet dispatched also becomes critical, if Ur packets it jumping too many routers, it will eventually get dropped if ur "ttl" value is low.

Basically, its a network-issue; for which Ur MIS team will need to help U with.

Cheers.

mandar_shindea at 2007-7-15 18:59:10 > top of Java-index,Other Topics,Java Community Process (JCP) Program...
# 2
Thank you very much.And can you give me a excemple about Sock5?It would be very helpful.Thank you!
fool_leavea at 2007-7-15 18:59:10 > top of Java-index,Other Topics,Java Community Process (JCP) Program...