代理服务器的源程序，只是一个示范，可以了解
Proxy原理
program:
proxyd
module:
proxyd.c
summary: provides
proxy tcp service for a host on an isolated network.
programmer: Carl Harris (ceharris@vt.edu)
date: 22 Feb 94
description:
This code implements a daemon process which listens for tcp connec-
tions on a specified port number. When a connection is established,
a child is forked to handle the new client. The child then estab-
lishes a tcp connection to a port on the isolated host. The child
then falls into a loop in which it writes data to the isolated host
for the client and vice-versa. Once a child has been forked, the
parent resumes listening for additional connections.
The name of the isolated host and the port to serve as
proxy for,
as well as the port number the
server listen on are specified as
