When I speak of a connection in HTTP, I refer to a TCP connection. As illustrated in Figure 3.1, a TCP connection requires three separate messages.

Figure 3.1. A TCP connection requires three messages.

SYN and ACK are two flags within the TCP segment of a packet. Because TCP is such a common transport layer protocol to be used in conjunction with IP, the combined packet of an IP packet containing a TCP segment is sometimes called a TCP/IP packet, even though it would best be described as a packet within a packet. By this example, you can see that a connection is unlike what you might otherwise expect. After this exchange, both computers ...

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