命名UNIX域套接字通信

《UNIX环境高级编程》中开发的三个函数 

#include "apue.h"
#include <sys/socket.h>
#include <sys/un.h>
#include <time.h>
#include <errno.h>

#define	STALE	30	/* client's name can't be older than this (sec) */

#define QLEN	10

#define	CLI_PATH	"./"
#define	CLI_PERM	S_IRWXU			/* rwx for user only */
/*
 * Wait for a client connection to arrive, and accept it.
 * We also obtain the client's user ID from the pathname
 * that it must bind before calling us.
 * Returns new fd if all OK, <0 on error
 */
int
serv_accept(int listenfd, uid_t *uidptr)
{
	int					clifd, err, rval;
	socklen_t			len;
	time_t				staletime;
	struct sockaddr_un	un;
	struct stat			statbuf;
	char				*name;

	/* allocate enough space for longest name plus terminating null */
	if ((name = malloc(sizeof(un.sun_path + 1))) == NULL)
		return(-1);
	len = sizeof(un);
	if ((clifd = accept(listenfd, (struct sockaddr *)&un, &len)) < 0) {
		free(name);
		return(-2);		/* often errno=EINTR, if signal caught */
	}

	/* obtain the client's uid from its calling address */
	len -= offsetof(struct sockaddr_un, sun_path); /* len of pathname */
	memcpy(name, un.sun_path, len);
	name[len] = 0;			/* null terminate */
	if (stat(name, &statbuf) < 0) {
		rval = -3;
		goto errout;
	}

#ifdef	S_ISSOCK	/* not defined for SVR4 */
	if (S_ISSOCK(statbuf.st_mode) == 0) {
		rval = -4;		/* not a socket */
		goto errout;
	}
#endif

	if ((statbuf.st_mode & (S_IRWXG | S_IRWXO)) ||
		(statbuf.st_mode & S_IRWXU) != S_IRWXU) {
		  rval = -5;	/* is not rwx------ */
		  goto errout;
	}

	staletime = time(NULL) - STALE;
	if (statbuf.st_atime < staletime ||
		statbuf.st_ctime < staletime ||
		statbuf.st_mtime < staletime) {
		  rval = -6;	/* i-node is too old */
		  goto errout;
	}

	if (uidptr != NULL)
		*uidptr = statbuf.st_uid;	/* return uid of caller */
	unlink(name);		/* we're done with pathname now */
	free(name);
	return(clifd);

errout:
	err = errno;
	close(clifd);
	free(name);
	errno = err;
	return(rval);
}



/*
 * Create a server endpoint of a connection.
 * Returns fd if all OK, <0 on error.
 */
int
serv_listen(const char *name)
{
	int					fd, len, err, rval;
	struct sockaddr_un	un;

	if (strlen(name) >= sizeof(un.sun_path)) {
		errno = ENAMETOOLONG;
		return(-1);
	}

	/* create a UNIX domain stream socket */
	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
		return(-2);

	unlink(name);	/* in case it already exists */

	/* fill in socket address structure */
	memset(&un, 0, sizeof(un));
	un.sun_family = AF_UNIX;
	strcpy(un.sun_path, name);
	len = offsetof(struct sockaddr_un, sun_path) + strlen(name);

	/* bind the name to the descriptor */
	if (bind(fd, (struct sockaddr *)&un, len) < 0) {
		rval = -3;
		goto errout;
	}

	if (listen(fd, QLEN) < 0) {	/* tell kernel we're a server */
		rval = -4;
		goto errout;
	}
	return(fd);

errout:
	err = errno;
	close(fd);
	errno = err;
	return(rval);
}



/*
 * Create a client endpoint and connect to a server.
 * Returns fd if all OK, <0 on error.
 */
int
cli_conn(const char *name)
{
	int					fd, len, err, rval;
	struct sockaddr_un	un, sun;
	int					do_unlink = 0;

	if (strlen(name) >= sizeof(un.sun_path)) {
		errno = ENAMETOOLONG;
		return(-1);
	}

	/* create a UNIX domain stream socket */
	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
		return(-1);

	/* fill socket address structure with our address */
	memset(&un, 0, sizeof(un));
	un.sun_family = AF_UNIX;
	sprintf(un.sun_path, "%s%05ld", CLI_PATH, (long)getpid());
printf("file is %s\n", un.sun_path);
	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;
		goto errout;
	}
	if (chmod(un.sun_path, CLI_PERM) < 0) {
		rval = -3;
		do_unlink = 1;
		goto errout;
	}

	/* fill socket address structure with server's address */
	memset(&sun, 0, sizeof(sun));
	sun.sun_family = AF_UNIX;
	strcpy(sun.sun_path, name);
	len = offsetof(struct sockaddr_un, sun_path) + strlen(name);
	if (connect(fd, (struct sockaddr *)&sun, len) < 0) {
		rval = -4;
		do_unlink = 1;
		goto errout;
	}
	return(fd);

errout:
	err = errno;
	close(fd);
	if (do_unlink)
		unlink(un.sun_path);
	errno = err;
	return(rval);
}

客户端：

#include "apue.h"
#include<stdio.h>
#include<unistd.h>
#include<string.h>
#include<stdlib.h>
#include<errno.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <sys/un.h>
//#include<netinet/in.h>
#define UNIXSOCKETNAME "test_socket"
#define ERR_EXIT(m) \
    do \
    { \
        perror(m); \
        exit(EXIT_FAILURE); \
    } while(0)
void echo_cli(int sock)
{
    char buf1[1024] = {0};
    char buf2[1024] = {0};
    int ret = 0;
    while(fgets(buf1, sizeof(buf1), stdin) != NULL)
    {
        write(sock, buf1, strlen(buf1));
        ret = read(sock, buf2, sizeof(buf2));
        if(ret == 0)
        {
            printf("server %d close\n", sock);
            break;
        }
        printf("%s", buf2);
        memset(buf1, 0, sizeof(buf1));
        memset(buf2, 0, sizeof(buf2));
    }
    close(sock);
}
int main()
{
   
    int sock = cli_conn(UNIXSOCKETNAME);
    if(sock < 0)
        ERR_EXIT("socket");
    
    echo_cli(sock);
    return 0;
}

服务器端：

#include "apue.h"
#include<stdio.h>
#include<unistd.h>
#include<string.h>
#include<stdlib.h>
#include<errno.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <sys/un.h>
#define ERR_EXIT(m) \
    do \
    { \
        perror(m); \
        exit(EXIT_FAILURE); \
    } while(0)
#define UNIXSOCKETNAME "./test_socket"
void echo_cli(int sock)
{
    char buf[1024] = {0};
    int ret = 0;
    while(1)
    {
        ret = read(sock, buf, sizeof(buf));
        if(ret == 0)
        {
            printf("client %d close\n", sock);
            break;
        }
        printf("server receive %s \n", buf);
        write(sock, buf, strlen(buf));
 	memset(buf, 0, sizeof(buf));
	
    }
    close(sock);
}
int main()
{
    int listenfd = serv_listen(UNIXSOCKETNAME);
    if(listenfd < 0)
        ERR_EXIT("socket");
    //unlink(UNIXSOCKETNAME);

    uid_t uidclient; 
    int conn;
    pid_t pid;
    while(1)
    {
	printf("server waiting ...\n");
	conn = serv_accept(listenfd, &uidclient);	
        if(conn == -1)
        {
            if(errno == EINTR)
                continue;
            ERR_EXIT("accept");
        }
        printf("Has new client connected, conn = %d\n", conn);
        pid = fork();
        if(pid < 0)
            ERR_EXIT("fork");
        else if(pid == 0)
        {            
            echo_cli(conn);
            exit(1);
        }
        else
            close(conn);
    }
    return 0;
}