Linux Efficiently test if a port is Open

Question

How can I quickly find out whether a port 445 is open/listening on a server from a bash script.

I have tried a couple of options, but I want something quick:
1. lsof -i :445 (Takes seconds)
2. netstat -an |grep 445 |grep LISTEN (Takes seconds)
3. telnet (it doesn't return)
4. nmap, netcat are not available on the server

Is there another way that doesn't enumerate first and greps after that.

Answer 1

$ nc -z <host> <port>; echo $?

Use this with 127.0.0.1 as "remote" address.