socket通信

1. 概念

1.1 C/C++中socket

#include <sys/socket.h>　
int socket(int family, int type, int protocol);   //指定期望的通信协议类型，返回的文件描述符和套接字描述符类似，我们称为套接字描述符，简称sockfd  

family：协议族

family	说明
AF_INET	IPv4协议
AF_INET6	IPv6
AF_LOCAL	Unix域协议
AF_ROUTE	路由套接字
AF_KEY	密钥套接字
AF_UNIX	本地通信

type:套接字的类型

type	说明
SOCK_STREAM	字节流套接字
SOCK_DGRAM	数据报套接字
SOCK_SEQPACKET	有序分组套接字
SOCK_RAW	原始套接字

protocol：协议类型的常量或设置为0，以选择给定的family和type组合的系统默认值

protocol	说明
IPPROTO_TCP	TCP传输协议
IPPROTO_UDP	UDP传输协议
IPPROTO_SCTP	SCTP传输协议

1.2 Android应用层socket

2. 本地通信代码（android和Linux的区别）

2.1 android和Linux下socket本地通信的区别

在Linux中的本地通信有两种方式：1.创建socket文件，通过文件与客户端socket通信；2.不创建socket文件

在android中无法创建socket文件（应该可以创建，只是我不知道怎么去创建而已）所以只能使用第二种不创建的方式

服务端示例代码：

#include <sys/types.h>  
#include <sys/socket.h>  
#include <stdio.h>  
#include <sys/un.h>  
#include <unistd.h>  
#include <stdlib.h> 
#include <stddef.h>


int main(){
    
    int fd;
    int client_fd;
    struct sockaddr_un server_address;// 套接字
    char ch_send, ch_recv;
    int server_len, client_len;
    int i;
    
    memset(&server_address, 0, sizeof(server_address));
    
    //必须删除，如果之前有这个文件，则会报错！
    unlink("server_socket");
    //1. 创建一个socket:本地通信协议；字节流方式;
    fd = socket(AF_UNIX, SOCK_STREAM, 0);
    printf("1
");
    //填充套接字
    server_address.sun_family = AF_UNIX;
    //这里是socket文件名，client就是用这个文件来通信
    //strcpy (server_address.sun_path, "server_socket");
    server_address.sun_path[0]='';
    strcpy (server_address.sun_path+1, "server_socket");
    //server_len = strlen(SERVER_NAME)  + offsetof(sockaddr_un, sun_path);  
    //printf("offsetof(struct sockaddr_un, sun_path)=%d
", offsetof(struct sockaddr_un, sun_path));
    server_len = offsetof(struct sockaddr_un, sun_path) + strlen(server_address.sun_path+1)+1;
    printf("server_len=%d
", server_len);
    printf("2
");
    //2. 绑定
    bind(fd, (struct sockaddr *)&server_address, server_len);
    printf("3
");
    //3. 被动接收listen
    listen (fd, 5);
    printf("4
");
    //4. 监听accept
    client_fd = accept(fd, (struct sockaddr *)&server_address, (socklen_t *)&client_len);
    printf("5
");
    //测试发送接收
    for (i = 0, ch_send = '1'; i < 5; i++, ch_send++) { 
        //没数据则会阻塞在这里
        printf("阻塞
");
        if (read (client_fd, &ch_recv, 1) == -1) {  
            perror ("read1");  
            exit (EXIT_FAILURE);  
        }
        printf ("服务端接收到的数据为： %c
", ch_recv);  
        
        sleep (1);  
        
        //发送数据
        if (write (client_fd, &ch_send, 1) == -1) {  
            perror ("read2");  
            exit (EXIT_FAILURE);  
        }  
    }  
    //关闭客户端socket连接
    close (client_fd);  
    unlink("server_socket");
}

客户端示例代码：

#include <sys/types.h>  
#include <sys/socket.h>  
#include <stdio.h>  
#include <sys/un.h>  
#include <unistd.h>  
#include <stdlib.h>  
#include <stddef.h>

int main (int argc, char *argv[])  
{  
    struct sockaddr_un address;  
    int sockfd;  
    int len;  
    int i, bytes;  
    int result;  
    char ch_recv, ch_send;  
      
    /*创建socket,AF_UNIX通信协议,SOCK_STREAM数据方式*/  
    if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {  
        perror ("socket");  
        exit (EXIT_FAILURE);  
    }  
      
    address.sun_family = AF_UNIX;  
    //strcpy (address.sun_path, "server_socket");  
    address.sun_path[0]='';
    strcpy (address.sun_path+1, "server_socket"); 
 
    //len = sizeof (address);  
    len = offsetof(struct sockaddr_un, sun_path) + strlen(address.sun_path+1)+1;
    /*向服务器发送连接请求*/  
    result = connect (sockfd, (struct sockaddr *)&address, len);  
        if (result == -1) {  
            printf ("ensure the server is up
");  
            perror ("connect");  
            exit (EXIT_FAILURE);  
    }  
      
    for (i = 0, ch_send = 'A'; i < 5; i++, ch_send++) {  
        if ((bytes = write(sockfd, &ch_send, 1)) == -1) { /*发消息给服务器*/  
            perror ("write");  
            exit (EXIT_FAILURE);  
        }  
          
        sleep (2); /*休息二秒钟再发一次*/  
          
        if ((bytes = read (sockfd, &ch_recv, 1)) == -1) { /*接收消息*/  
            perror ("read");  
            exit (EXIT_FAILURE);  
        }  
          
        printf ("客户端接收到的数据为： %c
", ch_recv);  
    }  
    close (sockfd);  
      
    return (0);  
}  

 

参考资料：

http://docs.huihoo.com/c/linux-c-programming/ch37s04.html

http://blog.csdn.net/ccwwff/article/details/45693469

http://www.xuebuyuan.com/726129.html