If I remember correctly one of them requires you to specify the port with -p separately, and the other gets it from -l. So it's nc -l 1234 on one, and nc -l -p

If I remember correctly one of them requires you to specify the port with -p separately, and the other gets it from -l. So it's nc -l 1234 on one, and nc -l -p 1234 on the other.