Content

| 7.3 |  | Troubleshooting TCP/IP Application Layer Protocols |
| 7.3.4 |  | Web traffic |

Hypertext Transfer Protocol (HTTP) is the protocol used to transfer the files that make up web pages. Although the HTTP specification allows for data to be transferred on port 80 using either TCP or UDP, most implementations use TCP.

HTTPS is a secure version of the HTTP protocol. Aside from the initial connection and setup, HTTPS and HTTP are basically the same. The difference lies in the initial setup between client and server. HTTPS uses the Secure Socket Layer (SSL) protocol. SSL was created in order to secure credit card purchases over the Internet. It requires that both sides of a connection be authenticated and that data be encrypted and decrypted. It uses port 443 to initiate a secure connection.

HTTP connectivity can be tested using any Telnet application that allows a port number to be specified by Telnetting to the IP address of the destination server using port 80.

- If the connection failed, a message will display stating that the Telnet application could not open a connection to the host on port 80.
- If the connection was successful, a hello message may be displayed or a Telnet window will open, but there will be no response. This indicates HTTP connectivity to the server. To have the Web server respond, type GET / HTTP/1.0, then press the enter key twice.

> Note: By default characters are not echoed in MS Telnet upon successful connection to a Web Server unless 'local echo' is enabled in the preferences.

The following table presents commands that can be used to troubleshoot a World Wide Web network application. A troubleshooter uses the information from these commands to isolate problems at the application layer that are related to the Web and the HTTP protocol.