The list has some 300 IP address or network. It means so many thousands of IP address

I wonder what reason one could have to try a port scan against such a large list. If you legally own (or use) that many systems, you should have a network management system making such strange scans unnecessary. I also wonder why you want to access machines owned by General Electrics (3.0.0.0/8) and the United States Department of Defense (22.0.0.0/8).

I don't know how nmap would be useful here.

Well, perhaps you should start reading the nmap documentation. nmap can be configured to scan entire net blocks. It can be configured to scan only one or a few selected ports. It can read a list of scan targets from a file. It can be configured to scan by establishing a TCP connection. It can scan in parallel. And it can be configured to do all this at once. And of course, nmap can write a report in various formats, like XML, HTML and plain text. nmap is the wheel you want to reinvent (and much more).

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

In reply to Re^3: Telnet list of IP and get information stored to a file by afoken
in thread Telnet list of IP and get information stored to a file by sanju7

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