There are several tools you can use to verify access to a remote network port: nc, tcping, telnet. Unfortunately, nc from the netcat package has been replaced by the one from nmap, which lacks the -z option, making it useless for non-interactive applications. The tcping still works, but it’s an add-on package and it’s old, so some time soon it may disappear. The telnet is probably not going anywhere, but it’s also an add-on and not good for automated queries.

The answer is to use an all-Bash solution as shown below. In case you’re wondering about the sleep and kill stuff, it is possible that the cat command will time out due to a firewall that quietly drops connections.

 

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