How to disable SSH timeout

SSH clients will automatically be disconnected from the server and prompt the below message after being idle or inactive for a while.

Read from remote host oseems.com: Connection reset by peer
Connection to oseems.com closed.

This is due to the SSH servers' configuration (often by default) to avoid hanging sessions and free up resources.

If you have administrative access to the SSH servers, you can configure it so that it will not easily disconnect idle sessions. This could be achieved by setting the parameters for TCPKeepAlive, ClientAliveInterval, and ClientAliveCountMax as per the following;

TCPKeepAlive no 
ClientAliveInterval 30
ClientAliveCountMax 240

SSH server configuration file is normally /etc/ssh/sshd_config. Restart the SSHd service for the changes to take effect.

What it basically means is that the server will not send the TCP alive packet to check if the client's connection is working, yet will still send the encrypted alive message every 30 seconds. It will only disconnect after at least 2 hours of inactivity.

The following is the full explanation for the options;

 TCPKeepAlive
         Specifies whether the system should send TCP keepalive messages to the other side.  If they are sent, death of the
         connection or crash of one of the machines will be properly noticed.  However, this means that connections will die
         if the route is down temporarily, and some people find it annoying.  On the other hand, if TCP keepalives are not
         sent, sessions may hang indefinitely on the server, leaving “ghost” users and consuming server resources.

         The default is “yes” (to send TCP keepalive messages), and the server will notice if the network goes down or the
         client host crashes.  This avoids infinitely hanging sessions.

         To disable TCP keepalive messages, the value should be set to “no”.

         This option was formerly called KeepAlive.

 ClientAliveCountMax
         Sets the number of client alive messages (see below) which may be sent without sshd(8) receiving any messages back
         from the client.  If this threshold is reached while client alive messages are being sent, sshd will disconnect the
         client, terminating the session.  It is important to note that the use of client alive messages is very different
         from TCPKeepAlive (below).  The client alive messages are sent through the encrypted channel and therefore will not
         be spoofable.  The TCP keepalive option enabled by TCPKeepAlive is spoofable.  The client alive mechanism is valu‐
         able when the client or server depend on knowing when a connection has become inactive.

         The default value is 3.  If ClientAliveInterval (see below) is set to 15, and ClientAliveCountMax is left at the
         default, unresponsive SSH clients will be disconnected after approximately 45 seconds.  This option applies to pro‐
         tocol version 2 only.

 ClientAliveInterval
         Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a
         message through the encrypted channel to request a response from the client.  The default is 0, indicating that
         these messages will not be sent to the client.  This option applies to protocol version 2 only.

If you don't have administrative access to the server, you can configure your SSH client to send the alive message to the server instead to achieve the same result. The key here is the ServerAliveInterval option for the SSH client.

You can do this by updating /etc/ssh/ssh_config (applying the setting to every user in the system) or in ~/.ssh/config (single user). Set the following option to have the client send the alive packet every 30 seconds to the server;

ServerAliveInterval 30

The other alternative is to manually set the ServerAliveInterval option every time you're connecting to a server by using the -o ServerAliveInterval=<time-in-second> prefix as the following example;

$ ssh -o ServerAliveInterval=30 user@example.com