HTTP: The Definitive Guide

TCP Connections

Just about all of the world’s HTTP communication is carried over TCP/IP, a popular layered set of packet-switched network protocols spoken by computers and network devices around the globe. A client application can open a TCP/IP connection to a server application, running just about anywhere in the world. Once the connection is established, messages exchanged between the client’s and server’s computers will never be lost, damaged, or received out of order.^[1]

Say you want the latest power tools price list from Joe’s Hardware store:

http://www.joes-hardware.com:80/power-tools.html

When given this URL, your browser performs the steps shown in Figure 4-1. In Steps 1-3, the IP address and port number of the server are pulled from the URL. A TCP connection is made to the web server in Step 4, and a request message is sent across the connection in Step 5. The response is read in Step 6, and the connection is closed in Step 7.

Figure 4-1. Web browsers talk to web servers over TCP connections

TCP Reliable Data Pipes

HTTP connections really are nothing more than TCP connections, plus a few rules about how to use them. TCP connections are the reliable connections of the Internet. To send data accurately and quickly, you need to know the basics of TCP.^[2]

TCP gives HTTP a reliable bit pipe . Bytes stuffed in one side of a TCP connection come out the other side correctly, and in ...