SSH: TIME_WAIT problem

The TIME_WAIT problem

Sometimes a forwarded port mysteriously hangs around after the forwarding SSH session has gone away. You try a command you've used successfully several times in a row and suddenly get an error message:

$ ssh1 -L2001:localhost:21 server.example.com
Local: bind: Address already in use

(This happens commonly if you're experimenting with port forwarding, trying to get something to work.) You know that you have no active SSH command listening on port 2001, so what's going on? If you use the netstat command to look for other listeners on that port, you may see a connection hanging around in the TIME_WAIT state:

$ netstat -an | grep 2001
tcp    0   0   127.0.0.1:2001   127.0.0.1:1472    TIME_WAIT

The TIME_WAIT state is an artifact of the TCP protocol. In certain situations, the teardown of a TCP connection can leave one of its socket endpoints unusable for a short period of time, usually only a few minutes. As a result, you cannot reuse the port for TCP forwarding (or anything else) until the teardown completes. If you're impatient, choose another port for the time being (say, 2002 instead of 2001) and get on with your work, or wait a short time for the port to become usable again.


source: http://www.unix.org.ua/orelly/networking_2ndEd/ssh/ch09_02.htm

p/s: This is why sometimes we faced this issue "Local: bind: Address already in use"