when I use telnet IP to connect my system after one week,it tells me that all port is in use and closed by remote side,please tell me what’s happened on my system,thanks a lot.

One telnet session for 1 week, or many telnet sessions over many weeks?
What is the server running exactly?
What does “pidin” show on the server, lots of shells?

“all port is in use”,what may cause that?indeed there 's one programme that using socket running on server,I’m sorry that I can’t use “pidin” for the server is one black-box without keyboard and CRT.

connect after a few days ( before you know it won’t work), then check with pidin or netstat .