quick check of open port

Question

The following is working as expected. (do not want to use nmap) I need to use nc (or any other built-in centOS) command in shell script to check the port 6379 of a remote server. I want the script to exit quickly if no response received in less than 1 second. But it seems that nc will wait for too long before quitting with exit code of 1

How do I "quickly" check if the port is listening?

# time nc -z 1.2.3.4 1234

real    0m21.001s
user    0m0.000s
sys 0m0.000s

# echo $?
1

# time nc -z 1.2.3.4 6379
Connection to 1.2.3.4 6379 port [tcp/*] succeeded!

real    0m0.272s
user    0m0.000s
sys 0m0.008s

# echo $?
0

score 3 · Accepted Answer · answered Mar 21 '12 at 10:14

3

nc has -w option for tuning the timeout. Try

time nc -w 1 -z 1.2.3.4 1234

answered Mar 21 '12 at 10:14

Janne Pikkarainen

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It's a shame it won't allow less than one second though ... – David Fraser Mar 07 '13 at 09:44

quick check of open port

1 Answers1