TCP协议是应用在传输层的协议。是一种面向连接的、可靠的协议。
TCP协议的特点：
1）面向字节流。
2）TCP是面向连接的运输层协议
3) 每一条TCP链接只能有两个端点
4）TCP提供可靠交付的服务
5）TCP提供全双工通信
根据TCP协议三次握手，server一直处于监听状态，等接受到client的请求连接（connect）信号，accept该连接。
server:
1 #include<stdio.h>
2 #include<string.h>
3 #include<unistd.h>
4 #include<stdlib.h>
5 #include<sys/socket.h>
6 #include<sys/types.h>
7 #include<netinet/in.h>
8 #include<arpa/inet.h>
9 #define _BACKLOG 5
10 void usage(char *_proc)
11 {
12 printf("usage: %s,[ip],[proc]",_proc);
13 }
14 int startup(const char *ip,const int port)
15 {
16 int sock = socket(AF_INET,SOCK_STREAM,0); //创建套接字
17 if(sock < 0)
18 {
19 perror("socket");
20 exit(1);
21 }
22 struct sockaddr_in local;
23 local.sin_family = AF_INET;
24 local.sin_port = htons(port);
25 local.sin_addr.s_addr = inet_addr(ip);
26 if(bind(sock,(struct sockaddr*)&local,sizeof(local))<0) //将IP和端口号绑定
27 {
28 perror("bind");
29 exit(2);
30 }
31 if(listen(sock,_BACKLOG)<0) //监听是否有进程与之创建连接
32 {
33 perror("listen");
34 exit(3);
35 }
36 return sock;
37 }
38 void* pthread(void * arg)
39 {
40 int sock = (int)arg;
41 char buf[1024];
42 while(1)
43 {
44 ssize_t size = read(sock,buf,sizeof(buf)-1);
45 if(size>0)
46 {
47 buf[size] = '\0';
48 }
49 else if(size==0)
50 {
51 printf("client close...\n");
52 break;
53 }
54 else
55 {
56 perror("read");
57 exit(3);
58 }
59 printf("client say: %s\n",buf);
60 }
61 close(sock);
62 return NULL;
63 }
64
65 int main(int argc,char *argv[])
66 {
67 if(argc != 3)
68 {
69 usage(argv[0]);
70 exit(1);
71 }
72 char *ip = argv[1];
73 int port = atoi(argv[2]);
74 int listen_sock = startup(ip,port);
75 struct sockaddr_in client;
76 socklen_t len = sizeof(client);
77 while(1)
78 {
79 int new_sock = accept(listen_sock,(struct sockaddr*)&client,&len);
80 if(new_sock<0)
81 {
82 perror("accept");
83 continue;
84 }
85 printf("get a client... sock %d,ip: %s,port: %d\n",new_sock,inet_nto a(client.sin_addr),ntohs(client.sin_port));
86 #ifdef _V1_ //单进程通信
87 char buf[1024];
88 while(1)
89 {
90 ssize_t size = read(new_sock,buf,sizeof(buf)-1);
91 if(size>0)
92 {
93 buf[size] = '\0';
94 }
95 else if(size==0)
96 {
97 printf("client close...\n");
98 break;
99 }
100 else
101 {
102 perror("read");
103 exit(3);
104 }
105 printf("client say :%s\n",buf);
106 }
107 #elif _V2_ //多进程
108 pid_t pid = fork();
109 if(pid<0)
110 {
111 perror("fork");
112 exit(4);
113 }
114 else if(pid == 0)
115 {//child
116 close(listen_sock);
117 char *_client = inet_ntoa(client.sin_addr);
118 char buf[1024];
119 while(1)
120 {
121 memset(buf,'\0',sizeof(buf));
122 ssize_t size = read(new_sock,buf,sizeof(buf)-1);
123 if(size>0)
124 {
125 buf[size] = '\0';
126 }
127 else if(size==0)
128 {
129 printf("[ip]:%s close...\n",_client);
130 break;
131 }
132 else
133 {
134 perror("read");
135 exit(3);
136 }
137 printf("[ip]:%s say :%s\n",_client,buf);
138 }
139 close(new_sock);
140 exit(0);
141 }
142 else
143 {//father
144 close(new_sock);
145 }
146 #elif _V3_ //多线程
147 pthread_t pid;
148 pthread_create(&pid,NULL,pthread,(void*)new_sock);
149 pthread_detach(pid);
150 #else
151 printf("default");
152 #endif
153 }
154 return 0;
155 }
client:
1 #include<stdio.h>
2 #include<unistd.h>
3 #include<stdlib.h>
4 #include<sys/socket.h>
5 #include<sys/types.h>
6 #include<netinet/in.h>
7 #include<arpa/inet.h>
8
9 void usage(char *proc)
10 {
11 printf("usage:%s,[remote ip],[remote proc]",proc);
12 }
13 int main(int argc,char *argv[])
14 {
15 if(argc != 3)
16 {
17 usage(argv[0]);
18 exit(1);
19 }
20 int sock = socket(AF_INET,SOCK_STREAM,0);
21 if(sock<0)
22 {
23 perror("sock");
24 exit(1);
25 }
26 int port = atoi(argv[2]);
27 char *ip = argv[1];
28 struct sockaddr_in remote;
29 remote.sin_family = AF_INET;
30 remote.sin_port = htons(port);
31 remote.sin_addr.s_addr = inet_addr(ip);
32
33 int ret = connect(sock,(struct sockaddr*)&remote,sizeof(remote));
34 if(ret<0)
35 {
36 perror("connect");
37 exit(2);
38 }
39 char buf[1024];
40 while(1)
41 {
42 printf("please say: ");
43 scanf("%s",buf);
44 ssize_t size = write(sock,buf,sizeof(buf)-1);
45
46 }
47 return 0;
48 }
结果：
[fbl@localhost tcp]$ ./tcp_server 192.168.1.106 8080
get a client... sock 4,ip: 192.168.1.106,port: 51708
client say: hello
client say: hi
client say: nihao
client close...
^C
[fbl@localhost tcp]$
[fbl@localhost tcp]$ ./tcp_client 192.168.1.106 8080
please say: hello
please say: hi
please say: nihao
please say: ^C
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