第一章 简介和TCP/IP

最近在看《Unix网络编程》打算记录下读书过程，用于鞭策自己不要懈怠。

搭建环境

首先是编译环境的搭建，我用的是vm 12 pro+centos7，然后下载源代码 unpv13e.tar.gz

然后解压源代码：tar -xzvf unpv13e.tar.gz

然后查看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.

接着按照顺序来执行上面的命令。

我在执行

cd ../libfree

make

之后出错了：

inet_ntop.c: In function ‘inet_ntop’:
inet_ntop.c:60:9: error: argument ‘size’ doesn’t match prototype
size_t size;
^
In file included from inet_ntop.c:27:0:
/usr/include/arpa/inet.h:64:20: error: prototype declaration
extern const char *inet_ntop (int __af, const void *__restrict __cp,
^
make: *** [inet_ntop.o] Error 1

于是，vim inet_ntop.c ，将第60行的 size_t size 改成 socklen_t size; ，再重新make即可。

接下来又出错：

[root@yao libfree]# cd ../libroute/
[root@yao libroute]# make
gcc -I../lib -g -O2 -D_REENTRANT -Wall   -c -o get_rtaddrs.o get_rtaddrs.c
In file included from get_rtaddrs.c:1:0:
unproute.h:3:45: fatal error: net/if_dl.h: No such file or directory
#include <net/if_dl.h>  /* sockaddr_sdl{} */
^
compilation terminated.
make: *** [get_rtaddrs.o] Error 1

好吧，先把编译问题放到一边，直接

[root@yao unpv13e]# cd intro/
[root@yao intro]# make daytimetcpcli
gcc -I../lib -g -O2 -D_REENTRANT -Wall   -c -o daytimetcpcli.o daytimetcpcli.c
gcc -I../lib -g -O2 -D_REENTRANT -Wall -o daytimetcpcli daytimetcpcli.o ../libunp.a -lpthread
[root@yao intro]# ./daytimetcpcli 127.0.0.1
connect error: Connection refused
[root@yao intro]# ./daytimetcpcli 127.0.0.1
connect error: Connection refused

然后发现daytime服务没开启，centos中开启daytime服务：

[root@yao intro]#  yum install xinetd
[root@yao intro]# vim /etc/xinetd.d/daytime-stream //*将disable改为no*
[root@yao intro]# vim /etc/xinetd.d/daytime-dgram //*将disable改为no*
[root@yao intro]# service xinetd restart
Redirecting to /bin/systemctl restart  xinetd.service
[root@yao intro]# ./daytimetcpcli 127.0.0.1
12 JUN 2016 10:28:58 CST

于是搞定了。

1.2

这里面的好多函数都是后面章节会介绍的，先了解一下。

#include    "unp.h"

int main(int argc, char **argv)
{
int                 sockfd, n;
char                recvline[MAXLINE + 1];
struct sockaddr_in  servaddr;

if (argc != 2)
err_quit("usage: a.out <IPaddress>");//作者编写的函数

if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
err_sys("socket error");

bzero(&servaddr, sizeof(servaddr));//清零
servaddr.sin_family = AF_INET;
servaddr.sin_port   = htons(13);    /* daytime server 端口 */
if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0)//将IP转换为合适的格式
err_quit("inet_pton error for %s", argv[1]);

if (connect(sockfd, (SA *) &servaddr, sizeof(servaddr)) < 0)//建立连接
err_sys("connect error");

while ( (n = read(sockfd, recvline, MAXLINE)) > 0) {
recvline
= 0;    /* null terminate */
if (fputs(recvline, stdout) == EOF)
err_sys("fputs error");
}
if (n < 0)
err_sys("read error");

exit(0);
}