Simple tcp server using netcat

netcat_tcp_server.sh

#!/bin/bash
# Simple tcp server using netcat
#  - depending on the netcat version either use nc -l 5555 or nc -l -p 5555
#  - verify with `telnet locahhost 5555`
#  - quit the telnet with `ctrl-]` and then type quit
#  - the while loop is there so reopen the port after a client has disconnected
#  - supports only one client at a time
PORT=5555;
while :; do nc -l -p $PORT | tee  output.log; sleep 1; done

I want the server accept connection from outside(global), not only from inside(localhost)

I guess you've already found out the solution.

For guys who come here later, you have to run this script on a public machine (having a public IP address) to make it accessible globally. Of course, the port on which nc is listening must be open as well (using ufw).

If that isn't the case, you can use a service like ngrok to make that port publicly available.

On OSX this is while :; do nc -l localhost $PORT | tee output.log; sleep 1; done (or use brew for conventional unix syntax)