socketpair通信

1、线程间通信（参考安卓源码InputTransport.cpp）

#include <pthread.h>
#include <sys/types.h>            /* See NOTES */
#include <sys/socket.h>
#include <stdio.h>
#include <unistd.h>

static const size_t SOCKET_BUFFER_SIZE =  * ;

void *pthread_1(void *arg)
{
    int fd = *((int *)arg);
    char buf[];
    int len;
    int cnt = ;

    while () {
        len = sprintf(buf, "hello, main pthread, cnt = %d", cnt++);
        write(fd, buf, len);

        len = read(fd, buf, );
        buf[len] = '\0';
        printf("%s\n", buf);
        sleep();
    }
    return NULL;
}

int main(int argc, char **argv)
{
    int sockets[];
    pthread_t thread_id;
    if (socketpair(AF_UNIX, SOCK_SEQPACKET, , sockets)) {
        printf("socketpair error\n");
        return -;
    }
    int bufferSize = SOCKET_BUFFER_SIZE;
    /* 创建4个buff, sockets[0]的发送buff和接收buff; sockets[1]的发送buff和接收buff*/
    setsockopt(sockets[], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
    int res = pthread_create(&thread_id, NULL, pthread_1, (void *)(&sockets[]));
    if (res) {
        printf("pthread_create error\n");
        return -;
    }
    int fd = sockets[];
    char buf[];
    int len;
    int cnt = ;

    while () {
        len = sprintf(buf, "hello, pthread1, cnt = %d", cnt++);
        write(fd, buf, len);  //将buf中的内容通过fd句柄发送到snd buff

        len = read(fd, buf, );   //通过读fd中的rcv buff， 将内容读到buf中，然后打印出来
        buf[len] = '\0';
        printf("%s\n", buf);
        sleep();
    }
    return ;
}

打印信息:

再打开一个终端查看进程：ps  -A 查看socketpair的pid为6065

cd /proc/6065

ls task

2、父子进程间通信

需要注意的是fd == 0是子进程，fd > 0 是父进程

#include <unistd.h>
#include <sys/types.h>            /* See NOTES */
#include <sys/socket.h>
#include <stdio.h>
#include <unistd.h>

static const size_t SOCKET_BUFFER_SIZE =  * ;

int main(int argc, char **argv)
{
    int sockets[];
    if (socketpair(AF_UNIX, SOCK_SEQPACKET, , sockets)) {
        printf("socketpair error\n");
        return -;
    }
    int bufferSize = SOCKET_BUFFER_SIZE;
    setsockopt(sockets[], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
    setsockopt(sockets[], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
     pid_t fd = fork();if (fd == ) {
        /* 子进程 */
        int fd = sockets[];
        char buf[];
        int len;
        int cnt = ;
        while () {
                len = sprintf(buf, "hello, father pid, cnt = %d", cnt++);
                write(fd, buf, len);

                len = read(fd, buf, );
                buf[len] = '\0';
                printf("%s\n", buf);
                sleep();
        }
     }
     if (fd > ) {
        /* 父进程 */
         int fd = sockets[];
        char buf[];
        int len;
        int cnt = ;
        while () {
                len = sprintf(buf, "hello, child pid, cnt = %d", cnt++);
                write(fd, buf, len);

                len = read(fd, buf, );
                buf[len] = '\0';
                printf("%s\n", buf);
                sleep();
        }

     }

     return ;
}

运行结果：

查看进程：ps -A   有2个名为fork的进程

3、使用binder传递文件句柄，实现进程间通信

4、看得出来socketpair实现了进程或线程间的双全工通信

而管道一般是半全工通信，要双全工就得创建2个管道

#include <unistd.h>
#include <stdio.h>

int main(int argc, char **argv)
{

    int fd[];   //fd[0]是读，fd[1]是写
    int fd2[];
    int res = pipe(fd);
    if (res) {
       printf("create pipe error\n");
       return -;
    }
    res = pipe(fd2);
    if (res) {
       printf("create pipe2 error\n");
       return -;
    }
    pid_t pid = fork();
    if (pid > ) {
       char buf[];
       int len;
       while () {
           len = sprintf(buf, "hello my child!");
           buf[len] = '\0';
           write(fd[], buf, len);
           len = read(fd2[], buf, );
           buf[len] = '\0';
           printf("%s\n", buf);
           sleep();
       }
    }
    else if (pid == ) {char buf[];
       int len;
       while () {
           len = read(fd[], buf, );
           buf[len] = '\0';
           printf("%s\n", buf);
           len = sprintf(buf, "hello my father!");
           buf[len] = '\0';
           write(fd2[], buf, len);
           sleep();
       }

    }

    return ;
}

同样pipe也可以用于线程间通信：

#include <unistd.h>
#include <stdio.h>
#include <pthread.h>

struct pipe_rw {
      int fd_r;
      int fd_w;
};

void *thread_handle(void *arg)
{
     struct pipe_rw *pPipeRw = (struct pipe_rw *)arg;
     char buf[];
     int len;
     while () {
         len = read(pPipeRw->fd_r, buf, );
        buf[len] = '\0';
        printf("%s\n", buf);
        len = sprintf(buf, "hello my father");
        buf[len] = '\0';
        write(pPipeRw->fd_w, buf, len);
        sleep();
     }
}

int main(int argc, char **argv)
{

    int fd[];   //fd[0]是读，fd[1]是写
    int fd2[];
    int res = pipe(fd);
    if (res) {
       printf("create pipe error\n");
       return -;
    }
    res = pipe(fd2);
    if (res) {
       printf("create pipe2 error\n");
       return -;
    }
    pthread_t thread;
    struct pipe_rw pipe_arg;
    pipe_arg.fd_r = fd[];
    pipe_arg.fd_w = fd2[];
    pthread_create(&thread, NULL, thread_handle, &pipe_arg);
    char buf[];
    int len;
    while () {
        len = sprintf(buf, "hello my child");
        buf[len] = '\0';
        write(fd[], buf, len);
        len = read(fd2[], buf, );
        buf[len] = '\0';
        printf("%s\n", buf);
        sleep();
    }

    return ;
}

命名管道：

write:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

#define PATH "./myfifo"

int main(int argc, char **argv)
{
    int res = mkfifo(PATH, |S_IFIFO);  //在当前目录下创建一个名为myfifo的管道
    if (res) {
       printf("create named pipe error\n");
       return -;
    }
    int fd = open(PATH, O_WRONLY);  //命名管道是可以直接open的
    if (fd < ) {
        printf("open %s error\n", PATH);
        return -;
    }
    char buf[];
    int len;
    len = sprintf(buf, "hello world");
    while () {
        write(fd, buf, len);
        sleep();
    }
    close(fd);
    return ;
}

read:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

#define PATH "./myfifo"    

int main(int argc, char **argv)
{
    int fd = open(PATH, O_RDONLY);
    if (fd < ) {
        printf("open %s error\n", PATH);
        return -;
    }
    char buf[];
    int len;
    while () {
        len = read(fd, buf, 512);
        buf[len] = '\0';
        printf("%s\n", buf);
    }
    close(fd);
    return ;
}