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The original instance is in the APUE (third edition) 17.2 UNIX domain socket

1. Use UNIX and sockets to poll XSI message queues (poll version, original version)

# include "apue.h" # include # define NQ 3 / / number of queues # define MAXMSZ 512 / / maximum message length # define KEY 0x123 / / the first key value of the message queue struct threadinfo {int qid; int fd;}; struct mymesg {long mtype Char mtext [MAXMSZ];}; void * helper (void * arg) {int n; struct mymesg m; struct threadinfo * tip = arg; for (;;) {printf ("helper qid% d, fd% d, tid% u\ n", tip- > qid, tip- > fd, (unsigned) pthread_self ()); memset (& m, 0, sizeof (m)) If ((n = msgrcv (tip- > qid, & m, MAXMSZ, 0, MSG_NOERROR))

< 0) { err_sys("msgrcv error"); } if (write(tip->

Fd, m.mtext, n)

< 0) { err_sys("write error"); } }}int main(){ int i, n, err; int fd[2]; int qid[NQ]; struct pollfd pfd[NQ]; struct threadinfo ti[NQ]; pthread_t tid[NQ]; char buf[MAXMSZ]; for (i = 0; i < NQ; ++i) { if ((qid[i] = msgget((KEY+i), IPC_CREAT|0666)) < 0) { //创建一个新队列 err_sys("msgget error"); } printf("queue %d ID is %d\n", i, qid[i]); if (socketpair(AF_UNIX, SOCK_DGRAM, 0, fd) < 0) { //创建UNXI域套接字（fd管道） err_sys("socketpair error"); } printf("fd[0]:%d\n", fd[0]); printf("fd[1]:%d\n", fd[1]); pfd[i].fd = fd[0]; pfd[i].events = POLLIN; ti[i].qid = qid[i]; ti[i].fd = fd[1]; if ((err = pthread_create(&tid[i], NULL, helper, &ti[i])) != 0) { //创建线程 err_exit(err, "pthread_create error"); } } for (;;) { if (poll(pfd, NQ, -1) < 0) { //等待事件发生 err_sys("poll error"); } for (i = 0; i < NQ; ++i) { //printf("i:%d\n", i); if (pfd[i].revents & POLLIN) { if ((n = read(pfd[i].fd, buf, sizeof(buf))) < 0) { err_sys("read error"); } buf[n] = 0; printf("queue %d id %d, message %s\n", i, qid[i], buf); } } } exit(0);} 编译命令： gcc pollmsg.c -o pollmsg -lapue -lpthread -std=c99 2、使用UNIX与套接字轮询XSI消息队列（epoll版，改版） #include "apue.h"#include #include #include #include #define NQ 3 //队列的数量#define MAXMSZ 512 //消息的最大长度#define KEY 0x123 //消息队列的第一个key值#define FDSIZE 1000#define EPOLLEVENTS 100struct threadinfo { int qid; int fd;};struct mymesg { long mtype; char mtext[MAXMSZ];};void *helper(void *arg){ int n; struct mymesg m; struct threadinfo *tip = arg; for (;;) { printf("helper qid %d, fd %d, tid %u\n", tip->

Qid, tip- > fd, (unsigned) pthread_self (); memset (& m, 0, sizeof (m)); if (n = msgrcv (tip- > qid, & m, MAXMSZ, 0, MSG_NOERROR))

< 0) { err_sys("msgrcv error"); } if (write(tip->

Fd, m.mtext, n) < 0) {err_sys ("write error");} int main () {int I, n, err; int fd [2]; int qid [NQ]; int epollfd; struct epoll_event events [EPOLLEVENTS]; struct threadinfo ti [NQ]; pthread_t tid [NQ] Char buf [MAXMSZ]; epollfd = epoll_create (FDSIZE); / / create epoll file descriptor for (I = 0; I < NQ; + + I) {if ((QID [I] = msgget ((KEY+i), IPC_CREAT | 0666) < 0) {/ / create a new queue err_sys ("msgget error") } printf ("queue% d ID is% d\ n", I, qid [I]); if (socketpair (AF_UNIX, SOCK_DGRAM, 0, fd) < 0) {/ / create UNXI domain socket (fd pipe) err_sys ("socketpair error");} struct epoll_event ev Ev.events = EPOLLIN; ev.data.fd = fd [0]; epoll_ctl (epollfd, EPOLL_CTL_ADD, fd [0], & ev); / / register fd [0] to epoll ti.qid = qid [I]; ti [I] .fd = fd [1] If ((err = pthread_create (& tid [I], NULL, helper, & ti [I])! = 0) {/ / create thread err_exit (err, "pthread_create error");}} for (;;) {int occurred If ((occurred = epoll_wait (epollfd, events, EPOLLEVENTS,-1) < 0) {/ / wait for the event to occur err_sys ("epoll error");} if (occurred = = 0) {err_sys ("epoll timeout") } for (I = 0; I < occurred; + + I) {if (events [I] .events & EPOLLIN) {if ((n = read (events [I] .data.fd, buf, sizeof (buf)) < 0) {err_sys ("read error")) } buf [n] = 0; printf ("main thread% u, message% s\ n", (unsigned) pthread_self (), buf);} exit (0);}

Compile command:

Gcc epollmsg.c-o epollmsg-lapue-lpthread-std=c99

3. Send messages to XSI message queue (test program, original)

# include "apue.h" # include # define MAXMSZ 512struct mymesg {long mtype; char mtext [MAXMSZ];}; int main (int argc, char * argv []) {key_t key; long qid; size_t nbytes; struct mymesg m; if (argc! = 3) {fprintf (stderr, "usage: sendmsg KEY message\ n"); exit (1) } key = strtol (argv [1], NULL, 0); / / printf ("key:0xX\ n", (unsigned) key); if ((qid = msgget (key, 0) < 0) {/ / Open an existing queue err_sys ("can't open queue key% s", argv [1]);} memset (& m, 0, sizeof (m)) Strncpy (m.mtext, argv [2], MAXMSZ-1); nbytes = strlen (m.mtext); m.mtype = 1; / / printf ("qid:%ld\ n", qid); if (msgsnd (qid, & m, nbytes, 0) < 0) {/ / send a message to the specified message queue err_sys ("can't send message") } exit (0);}

Compile command:

Gcc sendmsg.c-o sendmsg-lapue-std=c99

Related readings:

1. Summary of the differences among select, poll and epoll [collation]

2. The use of poll function, the original text

3. APUE Reading Notes

* walker * *

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