Open a test TCP connection to a specified IP/Port

Netcat

nc mail.server.net 25

(Windows version)

Socat

socat - TCP4:www.domain.org:80

(Windows version)

Reading socat's examples page never fails to boggle my mind.

pkgmgr is now replaced by dism.

Install telnet from command line (run it as administrator):

dism /online /Enable-Feature /FeatureName:TelnetClient

Then you can test TCP connection by:

telnet example.com 80

Just use Putty it's tiny (and has a portable app version). It lets you specify port and can use telnet which is a TCP connection. It also has other useful functions like serial connections (no hyper terminal in Windows 7), SSH, And Rlogin. It even has a RAW function that lets establish RAW TCP connections.

Also just so your aware: Telnet is included in XP, you can use it from the command line IE:

telnet mailserver.server.com 25

Which would establish a TCP connection on port 25.