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quick check of open port

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linux-howto

http://serverfault.com – 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 0m (HowTos)