fifo的双向通信的方式如下图：

两个进程间的通信需要两个命名管道，分别处理一个进程的读和写

导致这种通信方式出现的根因还是由于fifo的阻塞读和阻塞写，所以这里需要使用两个管道对读写进行分别处理。

同时因为管道传输的数据为流式数据，则无法对数据进行指定标记（数据的发送者，接受者，大小。。。）。

SERVER端代码如下：

/*************************************************************************> File Name: server.c> Author: > Mail: > Created Time: 三  9/25 08:34:44 2019************************************************************************/#include
#include
#include 
#include 
#include 
#include 
#include #define FIFO_SERVER "fifoserver"
#define FIFO_CLIENT "fifoclient"
int main()
{ mkfifo(FIFO_SERVER,0644);mkfifo(FIFO_CLIENT,0644);int server_fd,client_fd,ret;char server_buf[100], client_buf[100];ret = fork();if (ret == -1) { printf("fork failed
");_exit(-1);}//服务端的子进程用来写else if (ret == 0) { server_fd = open(FIFO_SERVER,O_WRONLY);if (-1 == server_fd) { printf("open FIFO_SERVER failed !
");_exit(-1);}while(1) { memset (server_buf , 0 ,100);scanf("%s",server_buf);write(server_fd,server_buf,strlen(server_buf));}close(server_fd);}//服务端的父进程用来读else { client_fd = open(FIFO_CLIENT,O_RDONLY);if (-1 == client_fd) { printf ("open FIFO_CLIENT failed 
");_exit(-1);}while (1) { memset(client_buf ,0 ,100);//不断if (read(client_fd, client_buf, 100) > 0) printf("server : %s
",client_buf);/*else {printf("read client_fd failed 
");_exit(-1);}*/}close(client_fd);} return 0;
}

CLIENT端代码如下：

/*************************************************************************> File Name: server.c> Author: > Mail: > Created Time: 三  9/25 08:34:44 2019************************************************************************/#include
#include
#include 
#include 
#include 
#include 
#include #define FIFO_SERVER "fifoserver"
#define FIFO_CLIENT "fifoclient"
int main()
{ //创建管道mkfifo(FIFO_SERVER,0644);mkfifo(FIFO_CLIENT,0644);int server_fd,client_fd,ret;char server_buf[100], client_buf[100];ret = fork();if (ret == -1) { printf("fork failed
");_exit(-1);}//客户端的子进程用来读else if (ret == 0) { server_fd = open(FIFO_SERVER,O_RDONLY);if (-1 == server_fd) { printf("open FIFO_SERVER failed !
");_exit(-1);}while(1) { memset (server_buf , 0 ,100);if (read(server_fd,server_buf,100) > 0) { printf("client:%s
",server_buf);}/*else {printf("read from server_fd failed 
");_exit(-1);}*/}close(server_fd);}//父进程用来写else { client_fd = open(FIFO_CLIENT,O_WRONLY);if (-1 == client_fd) { printf ("open FIFO_CLIENT failed 
");_exit(-1);}while (1) { memset(client_buf ,0 ,100);scanf("%s",client_buf);write(client_fd, client_buf, strlen(client_buf)); }close(client_fd);} return 0;
}

运行结果如下：