电子商务网站建设网站电子版,网站 改版 建议,在东莞怎么找工作,湖南旅游十大必去景区socket API原本是为网络通讯设计的#xff0c;但后来在socket的框架上发展出一种IPC机制#xff0c;就是UNIX Domain Socket。虽然网络socket也可用于同一台主机的进程间通讯#xff08;通过loopback地址127.0.0.1#xff09;#xff0c;但是UNIX Domain Socket用于IPC更有…socket API原本是为网络通讯设计的但后来在socket的框架上发展出一种IPC机制就是UNIX Domain Socket。虽然网络socket也可用于同一台主机的进程间通讯通过loopback地址127.0.0.1但是UNIX Domain Socket用于IPC更有效率不需要经过网络协议栈不需要打包拆包、计算校验和、维护序号和应答等只是将应用层数据从一个进程拷贝到另一个进程。这是因为IPC机制本质上是可靠的通讯而网络协议是为不可靠的通讯设计的。UNIX Domain Socket也提供面向流和面向数据包两种API接口类似于TCP和UDP但是面向消息的UNIX Domain Socket也是可靠的消息既不会丢失也不会顺序错乱。UNIX Domain Socket是全双工的API接口语义丰富相比其它IPC机制有明显的优越性目前已成为使用最广泛的IPC机制比如X Window服务器和GUI程序之间就是通过UNIXDomain Socket通讯的。使用UNIX Domain Socket的过程和网络socket十分相似也要先调用socket()创建一个socket文件描述符address family指定为AF_UNIXtype可以选择SOCK_DGRAM或 SOCK_STREAMprotocol参数仍然指定为0即可。UNIX Domain Socket与网络socket编程最明显的不同在于地址格式不同用结构体sockaddr_un表示网络编程的socket地址是IP地址加端口号而UNIX Domain Socket的地址是一个socket类型的文件在文件系统中的路径这个socket文件由bind()调用创建如果调用bind()时该文件已存在则bind()错误返回。以下程序将UNIX Domain socket绑定到一个地址。 size offsetof(struct sockaddr_un, sun_path) strlen(un.sun_path);
#define offsetof(TYPE, MEMBER) ((int)((TYPE *)0)-MEMBER) server #include stdlib.h
#include stdio.h
#include stddef.h
#include sys/socket.h
#include sys/un.h
#include sys/types.h
#include sys/stat.h
#include unistd.h
#include errno.h
#define QLEN 10
/*
* 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;
/* create a UNIX domain stream socket */
if ((fd socket(AF_UNIX, SOCK_STREAM, 0)) 0)
return(-1);
unlink(name); /* in case it already exists 否则bind的时候会出错*/
/* 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 会创建name*/
if (bind(fd, (struct sockaddr *)un, len) 0) {
rval -2;
goto errout;
}
if (listen(fd, QLEN) 0) { /* tell kernel were a server */
rval -3;
goto errout;
}
return(fd);
errout:
err errno;
close(fd);
errno err;
return(rval);
}
int serv_accept(int listenfd, uid_t *uidptr)
{
int clifd, len, err, 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); /* often errnoEINTR, if signal caught */
/* obtain the clients 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;
goto errout;
}
if (S_ISSOCK(statbuf.st_mode) 0) {
rval -3; /* not a socket */
goto errout;
}
if (uidptr ! NULL)
*uidptr statbuf.st_uid; /* return uid of caller */
unlink(un.sun_path); /* were done with pathname now */
return(clifd);
errout:
err errno;
close(clifd);
errno err;
return(rval);
}
int main(void)
{
int lfd, cfd, n, i;
uid_t cuid;
char buf[1024];
lfd serv_listen(foo.socket);
if (lfd 0) {
switch (lfd) {
case -3:perror(listen); break;
case -2:perror(bind); break;
case -1:perror(socket); break;
}
exit(-1);
}
cfd serv_accept(lfd, cuid);
if (cfd 0) {
switch (cfd) {
case -3:perror(not a socket); break;
case -2:perror(a bad filename); break;
case -1:perror(accept); break;
}
exit(-1);
}
while (1) {
r_again:
n read(cfd, buf, 1024);
if (n -1) {
if (errno EINTR)
goto r_again;
}
else if (n 0) {
printf(the other side has been closed.\n);
break;
}
for (i 0; i n; i)
buf[i] toupper(buf[i]);
write(cfd, buf, n);
}
close(cfd);
close(lfd);
return 0;
} client #include stdio.h
#include stdlib.h
#include stddef.h
#include sys/stat.h
#include fcntl.h
#include unistd.h
#include sys/socket.h
#include sys/un.h
#include errno.h
#define CLI_PATH /var/tmp/ /* 5 for pid 14 chars */
/*
* 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;
/* 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%05d, CLI_PATH, 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;
goto errout;
}
/* fill socket address structure with servers address */
memset(un, 0, sizeof(un));
un.sun_family AF_UNIX;
strcpy(un.sun_path, name);
len offsetof(struct sockaddr_un, sun_path) strlen(name);
if (connect(fd, (struct sockaddr *)un, len) 0) {
rval -4;
goto errout;
}
return(fd);
errout:
err errno;
close(fd);
errno err;
return(rval);
}
int main(void)
{
int fd, n;
char buf[1024];
fd cli_conn(foo.socket);
if (fd 0) {
switch (fd) {
case -4:perror(connect); break;
case -3:perror(listen); break;
case -2:perror(bind); break;
case -1:perror(socket); break;
}
exit(-1);
}
while (fgets(buf, sizeof(buf), stdin) ! NULL) {
write(fd, buf, strlen(buf));
n read(fd, buf, sizeof(buf));
write(STDOUT_FILENO, buf, n);
}
close(fd);
return 0;
} 转载于:https://www.cnblogs.com/xiangtingshen/p/10923350.html
