Networking – How to test HTTP (Port 80) using Telnet

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Telnet is a long-time favorite for troubleshooting connection issues. It can be used to attempt to connect to a server on a given port. Generally you can quickly ascertain whether sometime is "listening" on the remote side--which will confirm that

  • (1) you can get to the remote [gs server] from your test box, and…
  • (2) that a server is running and bound to the specified port you requested.

More specifically, telnet can be used to test HTTP scenarios, effectively stripping through all the friendly layers a browser usually hides from web visitor eyes. Troubleshooting HTTP using telnet is a great way to review exactly what is getting returned to your browser during a web request for a particular url. This allows you to see headers and collect other information related to the web server.

Here is a simple example making an HTTP 1.1 request. First, get to a command prompt. For example, if you are using Windows, Start -> Run -> cmd. (Though if you are using Windows, you may want to use something like CYGWIN, or Putty rather than the DOS prompt).

INPUT:

>telnet www.esqsoft.globalservers.com 80 

Note: this launches telnet and tells it to look up and connect to the server for "www.esqsoft.globalservers.com" on port 80.

OUTPUT:

Trying 64.136.56.122... Connected to www.esqsoft.globalservers.com. 
Escape character is '^]'. 

INPUT:

GET /index.htm HTTP/1.1 host: www.esqsoft.globalservers.com

Notes:

1) no OS cursor caret, the connection is open so you just get a blank line waiting for input.

2) need to hit <enter> twice after the "host:"

OUTPUT:

HTTP/1.1 200 OK
Date: Mon, 18 Apr 2005 16:38:00 GMT
Server: Apache/1.3.27 (Unix)  (Red-Hat/Linux) mod_ssl/2.8.12 OpenSSL/0.9.6 PHP/4.1.2 mod_perl/1.27 FrontPage/5.0.2.2623
Last-Modified: Thu, 01 Jul 2004 01:16:05 GMT
ETag: "158e008c-182c-40e365d5"
Accept-Ranges: bytes
Content-Length: 6188
Connection: close
Content-Type: text/html

...big long nasty HTML code here...
SOURCE

LINK (Esqsoft.com)

LANGUAGE
ENGLISH