check open network port with cat
cat < /dev/null > /dev/tcp/www.msn.com/89; echo $? cat < /dev/null > /dev/tcp/8.8.8.8/53; echo $?
What do you think?
Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?
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(echo > /dev/tcp/skinner/22) >/dev/null 2>&1 \&& echo "It's up" || echo "It's down" It's up(echo > /dev/tcp/skinner/222) >/dev/null 2>&1 && \echo "It's up" || echo "It's down" It's down The reason you want to wrap the echo > /dev/... in parentheses like this, (echo > /dev/...) is because if you don't, then with tests of connections that are down, you'll get these types of messages showing up.(echo > /dev/tcp/skinner/223) && echo hibash: connect: Connection refused bash: /dev/tcp/skinner/223: Connection refused These can't simply be redirected to /dev/null since they're coming from the attempt to write out data to the device /dev/tcp. So we capture all that output within a sub-command, i.e. (...cmds...) and redirect the output of the sub-command.