Ssh – Mosh doesn’t reconnect

moshssh

I installed mosh on a desktop and server yesterday (compiled latest v1.2.3 from source) and it works fine. I left the session open yesterday and have come into the office today to find my mosh session is dead, with the error along the top of the terminal window:

mosh: Last contact 14723 seconds ago. [To quit: Ctrl-^ .]

I thought mosh should auto reconnect, or do I have to manually tell it to reconnect? If so, how? Or, is it a setting I need to enabled somewhere, to auto reconnect?

I left an SSH session open to the same server, this is still working just fine.

Best Answer

Mosh will reconnect by default, no additional configuration should be done for that.

As for your case, I suspect one of the following:

mosh daemon has died on the server side for some reason. Check if it's still running.
Somehow the UDP port mosh uses has been blocked. It might be a problem in the router between the client and the server, or a problem in the network configuration on either side.

Related Solutions

SSH tunnel to router periodically hangs. TCP problem

Two guesses:

Packet loss. Do not trust the "ping" you ran in parallel since the packet loss may be affecting only those TCP streams, for whatever reason. One simple way to detect it is to run $ netstat -s -p|grep "segments retransmited" frequently on both sides (ssh client and server) during the SSH session. See if the counter increases, in which case you experienced packet loss on TCP sessions in this machine. That said, the best way is to use tcpdump or wireshark to record what is happening and confirm there are re-transmissions occurring (they are usually marked with red by wireshark, but YMMV).
MTU problems. If you're trying to list the content of a large directory via SSH, for example, it may occur that the amount of data being transmitted would require it to be fragmented. The endpoints will use path MTU detection to determine the amount of data to send at a time. But in some cases, a firewall in the path may be blocking all ICMP packets and therefore breaking the path MTU detection, causing apparent freezes. This can be hard to confirm and diagnose. The easiest workaround that always works is to change the MTU of the network interface in either side to a low value, such as 1200 or 1000. This may hurt your performance so you'd better not use this forever.

Ssh – Mosh to a specific remote shell

Try:

mosh user@host -- /path/to/some/shell

The general form is:

mosh [options] -- user@host [command]

If you don't specify a command, mosh spawn a login shell by default.

Best Answer

Related Solutions

SSH tunnel to router periodically hangs. TCP problem

Ssh – Mosh to a specific remote shell

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