Hi, I'm not sure if this is a bug or not, maybe someone noticed it also... I always do a remote port forwarding with openssh on 1026 port let's say ( ssh -R 1026:localhost:55555 ). Most times the port is opened on remote machine. But sometimes i notice that ssh can't do remote port forwarding to that port 1026. I looked on the remote machine (netstat -an) and no one is using that port, so the port is free. Only way to fix this is do a remote port forwarding to another port lets say 1056, successfully done, then try again and do it for 1026, this time remote port forwarding successfully works... Sometimes it works if i try again with 1026, but other times i need to open another port then try again with 1026 port... What can cause this instability to remote port forwarding? Is there another command than "netstat -an" to see if that port is really free or something is using it? If is a bug can it be fixed? I use version of OpenSSH 5.1p1 on remote machine and the client is OpenSSH for Windows 3.8.1p1 Thanks in advance, Adriana
Perhaps it is something wrong with your ssh client. I have had remote ssh port forwarding sessions open for weeks and in frequent use when using putty on the client and openssh 5.1 on the server. I have also had remote upon remote sessions going, which works, albiet a little slowly. IE Session1 client -> server1 -ssh -R 1080:server2:1080 -> server2 And Session2 client -putty remote port forwarding 1080 on server1 This allows me to access a web mgmt port for an app on server 2 which is sitting behind two firewalls that do not allowed to have web traffic in there. Very round about way of doing things. But it works Thanks Peter On 20/10/2009, at 1:31 AM, Adriana Rodean <adrya1984 at gmail.com> wrote:> Hi, > > I'm not sure if this is a bug or not, maybe someone noticed it also... > > I always do a remote port forwarding with openssh on 1026 port let's > say ( ssh -R 1026:localhost:55555 ). Most times the port is opened on > remote machine. But sometimes i notice that ssh can't do remote port > forwarding to that port 1026. I looked on the remote machine (netstat > -an) and no one is using that port, so the port is free. > Only way to fix this is do a remote port forwarding to another port > lets say 1056, successfully done, then try again and do it for 1026, > this time remote port forwarding successfully works... Sometimes it > works if i try again with 1026, but other times i need to open another > port then try again with 1026 port... > > What can cause this instability to remote port forwarding? > Is there another command than "netstat -an" to see if that port is > really free or something is using it? > If is a bug can it be fixed? > > I use version of OpenSSH 5.1p1 on remote machine and the client is > OpenSSH for Windows 3.8.1p1 > > Thanks in advance, > Adriana > _______________________________________________ > openssh-unix-dev mailing list > openssh-unix-dev at mindrot.org > https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
Hi, Here is some more info after little investigation :) Message i get is: "Warning: remote port forwarding failed for listen port 1026" SSH makes connection but port isn't opened and in server logs i see: IPP-Linux:~# cat /var/log/auth.log | grep 18722 Oct 19 13:37:20 IPP-Linux sshd[18722]: error: bind: Address already in use Oct 19 13:37:20 IPP-Linux sshd[18722]: error: channel_setup_fwd_listener: cannot listen to port: 1026 IPP-Linux:~# cat /var/log/auth.log | grep 18737 Oct 19 13:37:47 IPP-Linux sshd[18737]: error: bind: Address already in use Oct 19 13:37:47 IPP-Linux sshd[18737]: error: channel_setup_fwd_listener: cannot listen to port: 1026 But i closed the previous console with ssh listening to that port, and is no ssh process on client when i want to connect again on the same port. So how come it still says that port is in use on server? This happens in only 2% of the cases, very rare, i change nothing in the way i connect or close the client, but somehow it seems that port still hangs on server after closing ssh console ... or at least that's what sshd says because with "netstat -an" i don't see that port busy Thank you Rabbi for that command, next time when it happens i'll use it :) Thanks, Adriana
Thank you all for your replies :) This is the command i use: ssh -L 30300:localhost:8080 -R 1026:localhost:55555 -F ssh_config -N ipp at 10.55.40.120 And i close the ssh process by closing the windows console, or by killing the ssh process from another application. Either way when i look in processes list after closing ssh process is gone when i try to reconnect again. I guess that's the explanation suggested above why sometimes it doesn't allow me to reconnect with same port, TCP connection staying in a wait state even after previous ssh client process terminates and it keeps that remote port busy. Maybe that's why it didn't showed with "netstat -an" command. Next time i will use the other commands suggested :) Thank you again, Adriana