所需要頭文件 ：

#include

#include

函數(shù)格式 ：

int connect (int sockfd, struct sockaddr *serv_addr, int addrlen);

函數(shù)功能 ：

用來(lái)請(qǐng)求連接遠(yuǎn)程服務(wù)器，將參數(shù)sockfd的socket連至參數(shù)serv_addr所指定的服務(wù)器IP和端口號(hào)上去；

sockfd:客戶端的socket套接字

serv_addr:一個(gè)struct sockaddr類型的結(jié)構(gòu)體指針變量，存儲(chǔ)著遠(yuǎn)程服務(wù)器的IP與端口號(hào)信息

addrlen:結(jié)構(gòu)體變量的長(zhǎng)度

返回值 ：

若成功，返回0，否則返回-1，錯(cuò)誤信息存在errno中；

d. 發(fā)送

1            send_buf = send(sock_fd, send_buf, strlen(send_buf), 0);
2            if (send_buf <= 0)
3            {
4                fprintf(stderr,"send error:%s\\n\\a", strerror(errno));
5                close(sock_fd);
6                exit(1);
7            }

所需要頭文件 ：

#include

#include

函數(shù)格式 ：

int send(int sockfd, const void *buf, int len, int flags);

函數(shù)功能 ：

用來(lái)發(fā)送數(shù)據(jù)給指定的遠(yuǎn)端主機(jī)；

sockfd:客戶端的socket套接字

buf:指明一個(gè)緩沖區(qū)

len:指明緩沖區(qū)的長(zhǎng)度

flags:通常為0

返回值 ：

若成功，返回發(fā)送的字節(jié)數(shù)，否則返回-1，錯(cuò)誤信息存在errno中

d. 關(guān)閉socket

1    close(sock_fd);
2    exit(0);

3.3 TCP完整代碼

1/*
  2* tcp_server.c
  3# Copyright (C) 2017 hceng, 
  9#include 
 10#include 
 11#include       
 12#include 
 13#include 
 14#include 
 15#include 
 16#include 
 17#include 
 18#include 
 19#include 
 20
 21#define PORT_NUMBER 8888
 22#define BACKLOG     10
 23
 24/* socket->bind->listen->accept->send/recv->close*/
 25
 26int main(int argc, char **argv)
 27{
 28    int sock_fd, new_fd;
 29    struct sockaddr_in server_addr;
 30    struct sockaddr_in client_addr;
 31    int ret;
 32    int addr_len;
 33    int recv_len;
 34    unsigned char recv_buf[1000];
 35    int client_num = -1;
 36
 37    signal(SIGCHLD,SIG_IGN);
 38
 39    /* socket */
 40    sock_fd = socket(AF_INET, SOCK_STREAM, 0);//AF_INET:IPV4;SOCK_STREAM:TCP
 41    if (-1 == sock_fd)
 42    {
 43        fprintf(stderr,"socket error:%s\\n\\a", strerror(errno));
 44        exit(1);
 45    }
 46
 47    /* set server sockaddr_in */
 48    memset(&server_addr, 0, sizeof(struct sockaddr_in));//clear
 49    server_addr.sin_family = AF_INET;
 50    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);//INADDR_ANY:This machine all IP
 51    server_addr.sin_port = htons(PORT_NUMBER);
 52
 53    /* bind */
 54    ret = bind(sock_fd, (struct sockaddr *)(&server_addr), sizeof(struct sockaddr));
 55    if(-1 == ret)
 56    {
 57        fprintf(stderr,"bind error:%s\\n\\a", strerror(errno));
 58        close(sock_fd);
 59        exit(1);
 60    }
 61
 62    /* listen */
 63    ret = listen(sock_fd, BACKLOG);
 64    if (-1 == ret)
 65    {
 66        fprintf(stderr,"listen error:%s\\n\\a", strerror(errno));
 67        close(sock_fd);
 68        exit(1);
 69    }
 70
 71    /* accept */
 72    while(1)
 73    {
 74        addr_len = sizeof(struct sockaddr);
 75        new_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &addr_len);
 76        if (-1 == new_fd)
 77        {
 78            fprintf(stderr,"accept error:%s\\n\\a", strerror(errno));
 79            close(sock_fd);
 80            exit(1);
 81        }
 82
 83        client_num++;
 84        fprintf(stderr, "Server get connetion form client%d: %s\\n", client_num, inet_ntoa(client_addr.sin_addr));
 85
 86        if (!fork())
 87        {
 88            /* Child process */
 89            while (1)
 90            {
 91                /* recv */
 92                recv_len = recv(new_fd, recv_buf, 999, 0);
 93                if (recv_len <= 0)
 94                {
 95                    fprintf(stderr, "recv error:%s\\n\\a", strerror(errno));
 96                    close(new_fd);    
 97                    exit(1);
 98                }
 99                else
100                {
101                    recv_buf[recv_len] = '\\0';
102                    printf("Get msg from client%d: %s\\n", client_num, recv_buf);
103                }
104            }    
105            close(new_fd);            
106        }       
107    }
108
109    /* close */
110    close(sock_fd);
111    exit(0); 
112}

1/*
 2* tcp_client.c
 3# Copyright (C) 2017 hceng, 
 9#include 
10#include 
11#include 
12#include 
13#include 
14#include 
15#include 
16#include 
17#include 
18#include 
19
20#define PORT_NUMBER 8888
21
22/* socket->connect->send->close*/
23int main(int argc, char *argv[])
24{
25    int sock_fd;
26    struct sockaddr_in server_addr;
27    int ret;
28    unsigned char send_buf[1000];
29    int send_len;
30
31    if(argc != 2)
32    {
33        fprintf(stderr, "Usage:%s hostname\\n\\a", argv[0]);
34        exit(1);
35    }
36
37    /* socket */
38    sock_fd = socket(AF_INET, SOCK_STREAM, 0);//AF_INET:IPV4;SOCK_STREAM:TCP
39    if (-1 == sock_fd)
40    {
41        fprintf(stderr,"socket error:%s\\n\\a", strerror(errno));
42        exit(1);
43    }
44
45    /* set sockaddr_in parameter*/
46    memset(&server_addr, 0, sizeof(struct sockaddr_in));//clear
47    server_addr.sin_family = AF_INET;
48    server_addr.sin_port = htons(PORT_NUMBER);
49    ret = inet_aton(argv[1], &server_addr.sin_addr);
50    if(0 == ret)
51    {
52        fprintf(stderr,"server_ip error.\\n");
53        close(sock_fd);
54        exit(1);
55    }
56
57    /* connect */
58    ret = connect(sock_fd, (const struct sockaddr *)&server_addr, sizeof(struct sockaddr));    
59    if (-1 == ret)
60    {
61        fprintf(stderr,"connect error:%s\\n\\a", strerror(errno));
62        close(sock_fd);
63        exit(1);
64    }
65
66    while (1)
67    {
68        if (fgets(send_buf, 999, stdin))
69        {
70            /* send */
71            send_len = send(sock_fd, send_buf, strlen(send_buf), 0);
72            if (send_len <= 0)
73            {
74                fprintf(stderr,"send error:%s\\n\\a", strerror(errno));
75                close(sock_fd);
76                exit(1);
77            }
78        }
79    }
80
81    /* close */
82    close(sock_fd);
83    exit(0);
84}

3.4 測(cè)試結(jié)果

先在Ubuntu主機(jī)上交叉編譯服務(wù)器端代碼，再在Ubuntu主機(jī)上編譯客戶端代碼。

在開(kāi)發(fā)板上運(yùn)行服務(wù)器端代碼，在Ubuntu主機(jī)先啟動(dòng)tmux分屏，再分別運(yùn)行客戶端代碼。

• 服務(wù)器端
• 客戶機(jī)端