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Suppose I want to port scan my network. Normally I'll use a tool like nmap or nessus.

What if we don't have any tool to perform a Port Scan - how can we find open ports?

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No tools at all? Is telnet considered a tool? How about Windows? I think you need to better explain. – mikeazo Dec 17 '13 at 17:01
no, i don't have any automated tool to run port scan. I clarify again, i can not run any port scanner. telnet and windows are fine. – shekhar suman Dec 17 '13 at 17:07
Have you tried Googling for "online port scanner"? Just saying... – TildalWave Dec 17 '13 at 17:51
up vote 1 down vote accepted

Telnet to every possible port. See if you get a response back. If you know the protocol typically associated with the port you can manually send some commands and see what responses you get back.

For example you could telnet to port 80 on the target device and send a get request. See what comes back.

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you mean to say like, >telnet 80 So i need to do it for every suspected port?? – shekhar suman Dec 17 '13 at 17:16
@shekharsuman yes – mikeazo Dec 17 '13 at 17:42

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