功能：客户端向服务端发送字符串，服务端转化为大写发送给客户端
若想将服务端放在服务器上，客户端在本地访问，将服务端的监听套接字的ip绑定INADDR_ANY，而不能用127.0.0.1，客户端用服务器公网ip访问.
多进程版服务端：
1 #include<stdio.h>
2 #include<string.h>
3 #include<signal.h>
4 #include<unistd.h>
5 #include<stdlib.h>
6 #include<sys/socket.h>
7 #include<ctype.h>
8 #include<sys/types.h>
9 #include<wait.h>
10 #include<arpa/inet.h>
11 #include"wrap.h"
12 #define SERVER_IP "127.0.0.1"
13 #define SERVER_PORT 8008
14
15 void sighandler(int x)//捕捉函数回收子进程
16 {
17 while(waitpid(0,NULL,WNOHANG) >=0 );
18 }
19 int main(void)
20 {
21 int sfd,cfd;
22 pid_t pid;
23 struct sockaddr_in serv_addr,clien_addr;
24 socklen_t clien_len;
25 char buf[BUFSIZ];
26 signal(SIGCHLD,sighandler);//注册捕捉函数
27
28 sfd = Socket(AF_INET,SOCK_STREAM,0);//创建监听套接字
29
30 //填充serv_addr
31 serv_addr.sin_family = AF_INET;
32 serv_addr.sin_port = htons(SERVER_PORT);
33 //inet_pton(AF_INET,SERVER_IP,&serv_addr.sin_addr.s_addr);
34 serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
35
36 Bind(sfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr));//对sfd绑定ip和port
37 Listen(sfd,128);//设置允许同时连接上限
38
39 while(1)
40 {
41 char s[100];
42 clien_len = sizeof(clien_addr);
43 cfd = Accept(sfd,(struct sockaddr *)&clien_addr,&clien_len);
44 inet_ntop(AF_INET,&clien_addr.sin_addr.s_addr,s,sizeof(s));
45 pid = fork();
46 if(pid == 0)
47 {
48 close(sfd);//关闭父进程的监听套接字
49 int n;
50 while(1)
51 {
52 n = Read(cfd,buf,sizeof(buf));
53 if(n == 0)
54 {
55 close(cfd);
56 printf("port = %d exit\n",clien_addr.sin_port);
57 exit(1);
58 }
59 for(int i=0;i < n;i++)
60 buf[i] = toupper(buf[i]);
61 Write(cfd,buf,n);
62 }
63 }
64 else if(pid > 0)
65 {
66 printf("pid = %d ip = %s port = %d\n",pid,s,clien_addr.sin_port);
67 close(cfd);//关闭cfd
68 continue;
69 }
70 else{
71 perror("fork error");
72 exit(1);
73 }
74 }
75 return 0;
76 }
多线程版服务端：
1 #include"wrap.h"
2 #include<ctype.h>
3 #include<pthread.h>
4 #include<arpa/inet.h>
5 #define SERVER_PORT 8000
6 void *thread_func(void *arg)
7 {
8 long int cfd = (long int)arg;
9 char buf[BUFSIZ];
10 while(1)
11 {
12 int n;
13 n = Read(cfd,buf,sizeof(buf));
14 if(n == 0)
15 {
16 printf("exit\n");
17 close(cfd);
18 pthread_exit(NULL);
19 }
20 for(int i=0;i < n;i++)
21 buf[i] = toupper(buf[i]);
22 Write(cfd,buf,n);
23 }
24 }
25 int main(void)
26 {
27 pthread_t tid;
28 long int sfd,cfd;
29 struct sockaddr_in ser_addr,clt_addr;
30 socklen_t clt_addr_len = sizeof(clt_addr);;
31
32 sfd = Socket(AF_INET,SOCK_STREAM,0);//创建监听套接字
33
34 //绑定ip和port
35 ser_addr.sin_family = AF_INET;
36 ser_addr.sin_port = htons(SERVER_PORT);
37 ser_addr.sin_addr.s_addr = htonl(INADDR_ANY);
38
39 Bind(sfd,(struct sockaddr *)&ser_addr,sizeof(ser_addr));
40
41 Listen(sfd,128);//设置同时连接上限
42
43 while(1)
44 {
45 cfd = Accept(sfd,(struct sockaddr *)&clt_addr,&clt_addr_len);//阻塞监听
46 pthread_create(&tid,NULL,thread_func,(void *)cfd);//创建线程
47 pthread_detach(tid);//设置线程分离
48 }
49 close(sfd);
50
51 return 0;
52 }
客户端代码都一样，这里给出一份：
1 #include<stdio.h>
2 #include<unistd.h>
3 #include<string.h>
4 #include<arpa/inet.h>
5 #include<sys/socket.h>
6 #include<sys/types.h>
7 #include<stdlib.h>
8 #include"wrap.h"
9 #define SERVER_IP "127.0.0.1"
10 #define SERVER_PORT 8008
11 int main(void)
12 {
13 int cfd;
14 //int ret;
15 struct sockaddr_in server_addr;
16 int n;
17 char buf[BUFSIZ];
18
19 cfd = Socket(AF_INET,SOCK_STREAM,0);
20
21 memset(&server_addr,0,sizeof(server_addr));
22 server_addr.sin_family = AF_INET;
23 server_addr.sin_port = htons(SERVER_PORT);
24 inet_pton(AF_INET,SERVER_IP,&server_addr.sin_addr.s_addr);
25 Connect(cfd,(struct sockaddr *)&server_addr,sizeof(server_addr));
26
27 while(1)
28 {
29 n = Read(STDIN_FILENO,buf,sizeof(buf));
30 write(cfd,buf,n);
31 n = Read(cfd,buf,sizeof(buf));
32 write(STDOUT_FILENO,buf,n);
33 }
34 Close(cfd);
35 return 0;
36 }
代码中wrap.h为：
1 #ifndef __WRAP_H_
2 #define __WRAP_H_
3 #include<stdio.h>
4 #include<unistd.h>
5 #include<stdlib.h>
6 #include<sys/socket.h>
7 int Connect(int sockfd,const struct sockaddr *addr,socklen_t addrlen);
8 void perr_exit(const char *s);
9 int Socket(int domain, int type, int protocol);
10 int Bind(int sockfd,const struct sockaddr *addr,socklen_t addrlen);
11 int Listen(int sockfd,int backlog);
12 int Accept(int sockfd,struct sockaddr *addr,socklen_t *addrlen);
13 ssize_t Read(int fd,void *buf,size_t count);
14 ssize_t Write(int fd,const void *buf,size_t count);
15 int Close(int fd);
16 #endif
wrap.c为：
1 #include<stdio.h>
2 #include<unistd.h>
3 #include<stdlib.h>
4 #include<sys/socket.h>
5 void perr_exit(const char *s)
6 {
7 perror(s);
8 exit(1);
9 }
10 int Connect(int sockfd,const struct sockaddr *addr,socklen_t addrlen)
11 {
12 int ret;
13 if((ret = connect(sockfd,addr,addrlen)) == -1)
14 perr_exit("connect error");
15
16 return ret;
17 }
18 int Socket(int domain, int type, int protocol)
19 {
20 int fd;
21 if((fd = socket(domain,type,protocol)) == -1)
22 {
23 perr_exit("socket error");
24 }
25
26 return fd;
27 }
28
29 int Bind(int sockfd,const struct sockaddr *addr,socklen_t addrlen)
30 {
31 int ret;
32 if((ret = bind(sockfd,addr,addrlen)) == -1)
33 {
34 perr_exit("bind error");
35 }
36
37 return ret;
38 }
39
40 int Listen(int sockfd,int backlog)
41 {
42 int ret;
43 if((ret = listen(sockfd,backlog)) == -1)
44 {
45 perr_exit("listen error");
46 }
47
48 return ret;
49 }
50
51 int Accept(int sockfd,struct sockaddr *addr,socklen_t *addrlen)
52 {
53 int fd;
54 if((fd = accept(sockfd,addr,addrlen)) == -1)
55 {
56 perr_exit("accept error");
57 }
58
59 return fd;
60 }
61
62 ssize_t Read(int fd,void *buf,size_t count)
63 {
64 ssize_t n;
65 if((n = read(fd,buf,count)) == -1)
66 perr_exit("read error");
67
68 return n;
69 }
70
71 ssize_t Write(int fd,const void *buf,size_t count)
72 {
73 ssize_t n;
74 if((n == write(fd,buf,count)) == -1)
75 perr_exit("write error");
76
77 return n;
78 }
79
80 int Close(int fd)
81 {
82 int ret;
83 if((ret = close(fd)) == -1)
84 perr_exit("close error");
85
86 return ret;
87 }
