源代码下载地址http://www.unpbook.com/src.html
最近在看Unix网络编程，1.2节给了一个简单的客户端的例子，功能是利用TCP协议获取服务器的时间，我先把下载的源代码到Ubuntu上面，然后解压
tar -xzvf upv13e.tar.gz
打开解压的目录，发现有个readme文件
QUICK AND DIRTY ===============
Execute the following from the src/ directory:
./configure # try to figure out all implementation differences
cd lib # build the basic library that all programs need make # use "gmake" everywhere on BSD/OS systems
cd ../libfree # continue building the basic library make
cd ../libroute # only if your system supports 4.4BSD style routing sockets make # only if your system supports 4.4BSD style routing sockets
cd ../libxti # only if your system supports XTI make # only if your system supports XTI
cd ../intro # build and test a basic client program make daytimetcpcli ./daytimetcpcli 127.0.0.1
If all that works, you're all set to start compiling individual programs.
Notice that all the source code assumes tabs every 4 columns, not 8.
按照步骤，先执行 ./configure
再进入 lib目录 cd lib
make
进入libfree目录 cd ../libfree 然后 make
会有一些警告，忽略就行了，剩下两个make 不成功也没关系
后面最重要的一步
./daytimetcpcli 127.0.0.1后发现报错，Connection Refused
这个版本的Ubuntu默 认是不开daytime服务的，需要开启daytime服务，就在你当前的目录ls你可以看到有个daytimetcpsrv文件，执行sudo ./daytimetcpsrv。它的功能就是开启本机的daytime服务，然后你再开启一个终端，敲击./daytimetcpcli 127.0.0.1，就可以看见时间了
