Using python's telnetlib I can connect and communicate with a device.

While the telnet session is active I can disconnect the network cable of the device.

At this point, I would expect read_until() with a timeout to throw a socket.error, EOFError or perhaps an IOError, but what I actually get is a null string.

Because I'm reading in a loop, when the cable is reconnected the device will resume communicating, and the program will continue.

My best guess ts that read_until() or perhaps everything except open() is insensitive to the loss of a connection.