判断ip是否在线之linux下进程间通信（Unix domain socket）

1、程序实现的功能

（1）、程序pragram_a作为服务器，监听客户端发送过来的ip地址，服务端判断该ip地址是否在线
（2）、程序pragram_b作为客户端，向服务器发送ip地址，发送完后自行退出

2、代码实现

总共三个文件：pragram_a.c、pragram_b.c、makefile

//服务器源码：pragram_a.c
#include <stdio.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <stddef.h>
#include <string.h>
#include<stdlib.h>
#include<unistd.h>

// the max connection number of the server
#define MAX_CONNECTION_NUMBER 100

/* * Create a server endpoint of a connection. * Returns fd if all OK, <0 on error. */
int unix_socket_listen(const char *servername)
{
    int fd;
    struct sockaddr_un un;
    if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
    {
        return(-1);
    }
    int len, rval;
    unlink(servername);               /* in case it already exists */
    memset(&un, 0, sizeof(un));
    un.sun_family = AF_UNIX;
    strcpy(un.sun_path, servername);
    len = offsetof(struct sockaddr_un, sun_path) + strlen(servername);

    /* bind the name to the descriptor */
    if (bind(fd, (struct sockaddr *)&un, len) < 0)
    {
        rval = -2;
    }
    else
    {
        if (listen(fd, MAX_CONNECTION_NUMBER) < 0)
        {
            rval =  -3;
        }
        else
        {
            return fd;
        }
    }

    close(fd);
    return rval;
}

int unix_socket_accept(int listenfd, uid_t *uidptr)
{
    int clifd, len, rval;
    time_t staletime;
    struct sockaddr_un un;
    struct stat statbuf;

    len = sizeof(un);
    if ((clifd = accept(listenfd, (struct sockaddr *)&un, &len)) < 0)
    {
        return(-1);
    }

    /* obtain the client's uid from its calling address */
    len -= offsetof(struct sockaddr_un, sun_path);  /* len of pathname */
    un.sun_path[len] = 0; /* null terminate */
    if (stat(un.sun_path, &statbuf) < 0)
    {
        rval = -2;
    }
    else
    {
        if (S_ISSOCK(statbuf.st_mode))
        {
            if (uidptr != NULL) *uidptr = statbuf.st_uid;    /* return uid of caller */
            unlink(un.sun_path);       /* we're done with pathname now */
            return clifd;
        }
        else
        {
            rval = -3;     /* not a socket */
        }
    }

    close(clifd);

    return(rval);
}

void unix_socket_close(int fd)
{
    close(fd);
}

/* return 0 is online; return 1 is offline */
int ip_is_online(char* ip)
{
    char res[1024] = "ping -c2 -i0.2 -W1 ";
    strcat(res,ip);
    strcat(res, ">> server.log");

    return system(res);
}

int main(void)
{
    int listenfd;
    listenfd = unix_socket_listen("foo.sock");
    if(listenfd<0)
    {
        printf("Error[%d] when listening...\n",errno);
        return 0;
    }

    printf("\nServer is start\n");
    printf("=====================================================\n");
    printf("       ip                           status           \n");

    int size;
    char rvbuf[2048];
    while(1)
    {
        uid_t uid;
        int connfd;
        connfd = unix_socket_accept(listenfd, &uid);
        if(connfd<0)
        {
            printf("Error[%d:%s] when accepting...\n",errno,strerror(errno));
            break;
        }

        //===========接收==============
        memset(rvbuf,0,sizeof(char)*2048);
        size = recv(connfd, rvbuf, sizeof(rvbuf), 0);
        if(size>0)
        {
            if(ip_is_online(rvbuf) == 0)
            {
                printf("  %-20s              online\n",rvbuf);
            }
            else
                printf("  %-20s              offline\n",rvbuf);
        }
        if(size==-1)
        {
            printf("Error[%d] when recieving Data:%s.\n",errno,strerror(errno));
            break;
        }

        unix_socket_close(connfd);
    }

    unix_socket_close(listenfd);
    printf("Server exited.\n");
    return 0;
}

//客户端源码：pragram_b.c
#include <stdio.h>
#include <stddef.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

/* Create a client endpoint and connect to a server. Returns fd if all OK, <0 on error. */
int unix_socket_conn(const char *servername)
{
    int fd;
    if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)    /* create a UNIX domain stream socket */
    {
        return(-1);
    }

    int len, rval;
    struct sockaddr_un un;
    memset(&un, 0, sizeof(un));       /* fill socket address structure with our address */
    un.sun_family = AF_UNIX;
    sprintf(un.sun_path, "scktmp%5d",getpid());
    len = offsetof(struct sockaddr_un, sun_path) + strlen(un.sun_path);
    unlink(un.sun_path);               /* in case it already exists */
    if (bind(fd, (struct sockaddr *)&un, len) < 0)
    {
        rval = -2;
    }
    else
    {
        /* fill socket address structure with server's address */
        memset(&un, 0, sizeof(un));
        un.sun_family = AF_UNIX;
        strcpy(un.sun_path, servername);
        len = offsetof(struct sockaddr_un, sun_path) + strlen(servername);
        if (connect(fd, (struct sockaddr *)&un, len) < 0)
        {
            rval = -4;
        }
        else
        {
            return fd;
        }
    }

    close(fd);
    return rval;
}

void unix_socket_close(int fd)
{
    close(fd);
}

int main(int argc, char* argv[])
{
    int flag = 0;
    int k;
    for(k = 0; k < argc; k++)
    {
        if(strcmp(argv[k],"-c") == 0)
        {
            flag = 1;
            k++;
        }
        if(flag == 1)
        {
            int connfd = 0;
            connfd = unix_socket_conn("foo.sock");
            if(connfd<0)
            {
                printf("Error[%d] when connecting...",errno);
                return 0;
            }

            int size = 0;
            size = send(connfd, argv[k], strlen(argv[k]), 0);
            if(size > 0)
            {
                printf("send ip---->%s\n", argv[k]);
            }
            else if(size == -1)
            {
                printf("Error[%d] when sending data:%s.\n",errno, strerror(errno));
                break;
            }

            unix_socket_close(connfd);
            sleep(1);
        }
    }

    return 0;
}

#编译脚本：makefile
#This is the makefile of EpollTest

.PHONY:all
all:pragram_a pragram_b
server:
    gcc spragram_a.c -o pragram_a
client:
    gcc pragram_b.c -o pragram_b
clean:
    rm -f pragram_a pragram_b server.log foo.sock scktmp*

3、编译及运行结果

编译

运行

注：此程序在ubuntu和centos下运行正常