10 UNIX域协议

UNIX域套接字地址结构

#include <sys/un.h>

struct sockaddr_un {    sa_family sun_family;    char sun_path[104];}

套接字函数

1、路径最好是绝对路径，不要相对路径；

2、和connect调用中指定的路径名必须是一个当前绑定在某个打开的UNIX域套接字上的路径名，而且他们的套接字类型(字节流或数据报)也必须一致；

3、在一个未绑定的Unix域套接字上发送数据报不会自动给这个套接字捆绑一个路径名，这点不同于UDP套接字(对于UDP套接字，会自动绑定一个临时端口)，所以对于数据报UNIX域套接字客户端，则必须调用bind。

UNIX域字节流客户端/服务端

客户端：

#include <sys/un.h>#include <stdio.h>#include <string.h>#include <stdlib.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h> /*for struct sockaddr_in*/#define PATH "/home/unix_sock_xxxxx"#define MAX_BUF_LEN 255int main() {    int sockfd = 0;    sockfd = socket(AF_LOCAL, SOCK_STREAM, 0);    struct sockaddr_un addr;    memset(&addr, 0, sizeof(struct sockaddr_un));    addr.sun_family = AF_LOCAL;    strncpy(addr.sun_path, PATH, sizeof(addr.sun_path) - 1);        connect(sockfd, (struct sockaddr*)&addr, sizeof(addr));    printf("client is on...\n");         int i = 0;      for (i = 0; i < 5; i++)      {          char * msg = "hello server....";          printf("client send msg: %s\n", msg);          if((send(sockfd, msg, strlen(msg), 0))<0)          {              perror("send()");          }              char recv_buf[MAX_BUF_LEN] = {0};          int recv_len = recv(sockfd, recv_buf, sizeof(recv_buf), 0);          printf("client recv msg: %s\n", recv_buf);        }     return 1;}

服务端：

#include <sys/un.h>#include <stdio.h>#include <string.h>#include <stdlib.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h> /*for struct sockaddr_in*/#define PATH "/home/unix_sock_xxxxx"#define BACKLOG   10  #define MAX_BUF_LEN 255int main() {    int listenfd = 0;    int connfd   = 0;    struct sockaddr_un svr_addr;    struct sockaddr_un cli_addr;    memset(&svr_addr, 0, sizeof(struct sockaddr_un));    memset(&cli_addr, 0, sizeof(struct sockaddr_un));    listenfd = socket(AF_LOCAL, SOCK_STREAM, 0);    unlink(PATH);    svr_addr.sun_family = AF_LOCAL;    strncpy(svr_addr.sun_path, PATH, sizeof(svr_addr.sun_path) - 1);        bind(listenfd, (struct sockaddr*)&svr_addr, SUN_LEN(&svr_addr));    listen(listenfd, BACKLOG);    printf("server is on...\n");          int cli_len = sizeof(cli_addr);    connfd = accept(listenfd, (struct sockaddr*)&cli_addr, &cli_len);        char recv_buf[MAX_BUF_LEN] = {0};      int recv_len = 0;    while((recv_len = recv(connfd, recv_buf, sizeof(recv_buf), 0)) > 0)      {          printf("svr %d recv %s recv_len %d\n", connfd, recv_buf, recv_len);          int ret = send(connfd, recv_buf, strlen(recv_buf), 0);          if (ret < 0)          {              perror("send failed");              exit(1);          }          memset(recv_buf, 0, sizeof(recv_buf));      }          return 1;}

总结：和普通tcp套接字相比，不同点有family为AF_LOCAL，地址类型为sockaddr_un，同时宏SUN_LEN返回的是不包括空字符的结构体长度。其它基本一样。