1) Prepare a notepad window with the HTTP request codes that you want to run;
GET / HTTP/1.1
2) Copy the commands to the clipboard;
3) Open command prompt and telnet;
telnet www.google.com 80
4) Paste the HTTP code by right-clicking; then hit enter a couple times;
Note that you will get a blank screen (unless you have full duplex connection) and will not see the keystrokes that you enter.
At this point you will see a stream of text fill the screen. You should be able to scroll back in the command prompt window; you may need to change the command prompt properties to scroll all the way back.
Debug Browser Requests
Your browser will pass many headers in each request it makes. In the past, we used to have to run HTTP monitoring tools to see what the browser was doing, but now Firefox has a great add-on called Live HTTP Headers that makes it much easier.
There are several protocols that can be used in telnet, here is a list of ones I have used:
|SMTP (email sending)||25|
|FTP (file transfer)||21|
|POP3 (fetch messages)||110|
|IMAP (email server)||143|
Other online HTTP testing tools
Pingdom is great as it shows time to first/last byte
Uptrends - several geographical sources to test from.