Easy Tunnel

nc-test.exp

#!/usr/local/bin/expect

log_user 0
spawn nc localhost 2000
stty raw -echo
interact -o -nobuffer

open-mongo-connection.exp

#!/usr/local/bin/expect

log_user 0

proc username {} { return "my_user_name" }
proc first_ssh {} { return "ssh server1" }
proc second_ssh {} { return "ssh server2" }
proc third_nc {} { return "nc db_host db_port" }
spawn "[first_ssh]"

expect {
    "*[username]@host-*:~$ " {
        send "[second_ssh]; exit\n"
        expect {
            "*Last login:*(*:* *app-*:*~*) " {
                send "[third_nc]; exit\n"
                interact
            }
        }
    }
}

test-scenario.sh

# terminal 1
nc -l 2000

# terminal 2
socat tcp-l:200 system:'./nc-test.exp'

# terminal 3
nc localhost 200
# when I write something and hit enter, it echoes back; this is what I see
# 1
# 1
# hello
# hello