Probe a port with nc
nc to probe a port to test service availability or to check if portforwarding is working etc.
nc <hostname or ip> <port>
$ nc 192.168.1.111 22 SSH-2.0-OpenSSH_6.0p1 Debian-4 ^C
Simple Netcat Chat:
Requires 2 computers, one of which (A) must be running sshd, the other (B) must be capable of a client ssh connection. (A) must have netcat
Client (B) connects via ssh to (A)
The server (A) creates a netcat listener on any open port with:
nc -l -p 4444
Client connnects to that port with the following command issued into ssh:
nc localhost 4444
Clients and server should now be able to send plain text messages to each other via netcat. These messages are encrypted within the ssh tunnel.