wTCP客户端和服务器是如何通过TCP套接字接口进行通讯的。服务器距离、负载，网络拥堵。
HTTP The Definitive Guide
We begin with the web server waiting for a connection (Figure 4-6, S4). The client determines the IP
address and port number from the URL and proceeds to establish a TCP connection to the server
(Figure 4-6, C3). Establishing a connection can take a while, depending on how far away the server is,
the load on the server, and the congestion of the Internet.
Once the connection is set up, the client sends the HTTP request (Figure 4-6, C5) and the server reads
it (Figure 4-6, S6). Once the server gets the entire request message, it processes the request, performs
the requested action (Figure 4-6, S7), and writes the data back to the client. The client reads it (Figure
4-6, C6) and processes the response data (Figure 4-6, C7).