我不明白为什么下一个程序块..我在做什么错？

问题描述

下一个代码（改编自Rochkind的书），展示了一个客户端服务器应用程序，该应用程序将unix套接字与客户端和服务器一起使用unix套接字，并通过使用fork的父子关系进行关联。由于某种原因，程序被阻止了，我不知道为什么。该程序将打印以下行

[Server] ==> Socket 3 has been created
[Server] ==> Socket 3 has been boud to address
[Server] ==> Listening for incoming messages
[Client] ==> Socket 3 has been created
[Client] ==> Connection has been established .. let us write to server
[Server] ==> let us read from client
[Client] ==> 7 bytes written to server
[Client] ==> Now let us read from server

然后阻止。谁能帮助我检测到错误？非常感谢。

#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>

#define SOCKETNAME "MySocket"

int main(void) {
    struct sockaddr_un sa;
    (void)unlink(SOCKETNAME);
    strcpy(sa.sun_path,SOCKETNAME);
    sa.sun_family = AF_UNIX;
    int fd_skt,fd_client; char buf[100]; 
    int written; ssize_t readb;
    if (fork() == 0) { /* client */
        if ((fd_skt = socket(PF_UNIX,SOCK_STREAM,0)) < 0) {
             perror("Message from socket [client] : ");
             exit(-1); }        
        printf ("[Client] ==> Socket %d has been created\n",fd_skt);

        // Since cliend and server run concurrently,it is possible for the client
        // to call connect before the creation of the socket file by the server (ENOENT).
        // In this case the function sleeps for a second and tries again. If something
        // else goes wrong,the function fails.
        while (connect(fd_skt,(struct sockaddr *)&sa,sizeof(sa)) == -1) {
            if (errno == ENOENT) {
                sleep(1); continue; }
            else {
             perror("Message from connect [client]");
             exit(-2); }}

        // After connection the client and the server can communicate each other
        // using read and write functions 
        printf ("[Client] ==> Connection has been established .. let us write to server\n");
        written = write(fd_skt,"Hello!",7);
        if (written==-1) {
             perror("Message from write [client]");
             exit(-3); }
        else printf ("[Client] ==> %d bytes written to server\n",written);
        printf ("[Client] ==> Now let us read from server\n");             
        readb = read(fd_skt,buf,sizeof(buf));
        if (readb==-1) {
            perror("Message from read [client]");
             exit(-4); } 
        printf("Client got %s\n",buf);
        close(fd_skt);
        exit(0); }

    else { /* server */
         if ((fd_skt = socket(PF_UNIX,0)) < 0) {
              perror("Message from socket [server]");
              exit(-1); }    

        printf ("[Server] ==> Socket %d has been created\n",fd_skt);
        if (bind(fd_skt,(struct sockaddr *) &sa,sizeof(sa))){
            perror("Message from bind [server]");
            exit(-2); }    
        printf ("[Server] ==> Socket %d has been boud to address\n",fd_skt);                
        if (listen(fd_skt,5)){
            perror("Message from listen [server]");
            exit(-3); }
        printf ("[Server] ==> Listening for incoming messages\n");    
        if (fd_client = accept(fd_skt,NULL,0)<0) {
            perror("Message from accept [server]"); 
            exit(-4); }
        printf ("[Server] ==> let us read from client\n");            
        if (read(fd_client,sizeof(buf))==-1) {
             perror("Message from read [server] : ");
             exit(-5); } 
        printf("Server got %s\n",buf);
        printf ("[Server] ==> let us write to client\n");           
        if (write(fd_client,"Goodbye!",9)==-1) {
             perror("Message from write [server]");
             exit(-6); } 
        close(fd_skt);
        close(fd_client);
        exit(0); }}

解决方法

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