Sometimes we need to check if a certain TCP port is open. The following are some ways to do it.
$ netstat -an | grep 5100
*.5100 *.* 0 0 4000000 0 LISTEN
*.5100 *.* 0 0 4000000 0 LISTEN
*.5100 *.* 0 0 4000000 0 LISTEN
SUCCESS:
$ echo | telnet server_name 5100
Trying 100.10.10.10...
Connected to server_name.
Escape character is '^]'.
Connection to server_name closed by foreign host.
FAIL:
$ telnet server_name 5100
Trying 100.10.10.10...
telnet: Unable to connect to remote host: Connection refused
