socat pty,echo=0 terminal option does not work

I'd use socat to redirect the STDIN/STDOUT of the process executing docker run -it ubuntu bash command to a tcp socket in listening on port 32000. root@eve-ng:~# socat -d -d -d EXEC:'docker run -it ubuntu bash',pty,echo=0 TCP4-LISTEN:32000 From another terminal root@eve-ng:~# nc -v 127.0.0.1 32000 Connection to 127.0.0.1 32000 port [tcp/*] succeeded! root@ada2551fd122:/# ls /usr ls /usr bin games include lib lib64 libexec local sbin share src root@ada2551fd122:/# As you can see, the connection takes place and the command ls /usr executed within the container. The problem I'm facing to is that ls /usr like any other command entered is echoed back *twice*. As far as I can tell, the option echo=0 is there to prevent this behavior, however it doesn't seem to work as expected. What is actually going on ? Thanks.