nc
$ nc [--length ] [--listen] [-N] [-n] [--udp] [-p port] [--verbose] [target] [port]Network cat: Connect to network sockets as if it were a file.
-I, --length: Set maximum tcp receive buffer size-l, --listen: Listen instead of connecting-N: Close connection after reading stdin to the end-n: Suppress name resolution-u, --udp: UDP mode-p port: Local port for remote connections-v, --verbose: Log everything that's happening-z, --test-listening-service: Test a TCP-listening servicetarget: Address to listen on, or the address or hostname to connect toport: Port to connect to or listen on