fwrite() 阻止调用并且不写入文件

Question

我有一个 TCP Concurent 服务器，但我的客户端有问题 side.I 我正在尝试将文件从服务器发送到客户端，但客户端不会保存到文件，我猜 fwrite() 电话是罪魁祸首。

服务器代码：

 while (1)
{
    /* pregatirea structurii client */
  len = sizeof (from);
  bzero (&from, sizeof (from));

  /* a venit un client, acceptam conexiunea */
  client = accept (sd, (struct sockaddr *) &from, &len);

  /* eroare la acceptarea conexiunii de la un client */
  if (client < 0)
    {
      perror ("[server] Eroare la accept().\n");
      continue;
    }

      if (nr>30) 
    {
      char maxMsg[100]="Numarul maxim de participanti a fost atins.\n";
      write(client,maxMsg,50);
          close(client);
      nr--;
}
  else  
    {
      printf("[server] S-a conectat clientul cu descriptorul %d, de la adresa %s.\n",client, conv_addr (from));
      nr++;
    }
  fflush (stdout);

pid=fork();
if(pid<0)
  {
    printf ("[server] Eroare la fork().\n");
  }
if(pid==0)
  {
    /* copil/client  */
        if (welcome(client))
      {
        sendTest(client);
    printf ("[server] S-a deconectat clientul cu descriptorul %d.\n",client);
            fflush (stdout);
    close (client);     /* inchidem conexiunea cu clientul */
        nr--;
    close(sd);
    exit(0);
      }
  }

}               /* while */
}               /* main */
int welcome(int client)
{
 char buffer[100];      /* mesajul */
 int bytes;         /* numarul de octeti cititi/scrisi */
char name[100];     //mesajul primit de la client 
char msgrasp[100]=" ";        //mesaj de raspuns pentru client

bytes = read (client, name, sizeof (buffer));
if (bytes < 0)
{
  perror ("Eroare la read() de la client.\n");
  return 0;
}
printf ("[server] Numele participantului este %s\n", name);

/*pregatim mesajul de raspuns */
bzero(msgrasp,100);
strcat(msgrasp,"Hello ");
int ln = strlen(name) - 1;
if (name[ln] == '\n') 
name[ln] = '[=10=]';
strcat(msgrasp,name);
strcat(msgrasp,". Please wait for your test.\n");

printf("[server]Trimitem mesajul inapoi...%s\n",msgrasp);

if (bytes && write (client, msgrasp, bytes) < 0)
{
  perror ("[server] Eroare la write() catre client.\n");
  return 0;
}

return bytes;
}


int sendTest(int client)
{
FILE *fd;
int rand;
char filename[100];
char buffer[256];
int nread;

/* pregatim fisierul/testul pentru trimitere  */
bzero(filename,100);
rand = randInt();
sprintf(filename,"%d",rand);
strcat(filename,".c");

fd = fopen(filename, "r");
 if (fd == NULL)
   {
     perror("[server] Eroare la open().\n");
     exit(EXIT_FAILURE);
   }

/* trimitem numele fisierului */ 
write(client,filename,sizeof(filename));
printf("name=%s\n",filename);

/* Sending file data */
nread=fread(buffer,1,256,fd);
if(nread>0)
 {
  printf("[server] Sending file.\n");
  write(client,buffer,nread);
}

if (nread < 256)
{
  if (feof(fd))
    printf("End of file\n");
  if (ferror(fd))
    printf("Error reading\n");
}

fclose(fd);

return 0;
}

客户代码：

if (connect (sd, (struct sockaddr *) &server,sizeof (struct sockaddr)) == -1)
 {
  perror ("[client]Eroare la connect().\n");
  return errno;
 }

 /* citirea mesajului */
 bzero (name, 100);
 printf ("[client]Introduceti un nume: ");
 fflush (stdout);
 read (0, name, 100);

 /* trimiterea mesajului la server */
 if (write (sd, name, 100) <= 0)
 {
  perror ("[client]Eroare la write() spre server.\n");
  return errno;
 }

 /* citirea raspunsului dat de server 
 (apel blocant pina cind serverul raspunde) */
 if (read (sd, name, 100) < 0)
 {
  perror ("[client]Eroare la read() de la server.\n");
  return errno;
 }
 /* afisam mesajul primit */
 printf ("[client]Mesajul primit este: %s\n", name);
 fflush(stdout);

 /* primim numele fisierului  */
 read(sd,filename,sizeof(filename));
 fflush(stdout);

 char filename2[50]="test2.c";
 received_file = fopen(filename2, "w+");
 if (received_file == NULL)
 {
  printf("Eroare la fopen().\n");
  exit(EXIT_FAILURE);
 }

 bzero(recvBuff,256);
 while((bytesReceived = read(sd, recvBuff, 256)) > 0)
 {
    printf("Bytes received %d\n",bytesReceived);
    //fwrite(recvBuff, 8,bytesReceived,received_file);
    fwrite("asdf",4,1,received_file);
    printf("writing");
 }
 printf("wrote");
 fclose(received_file);
 printf("closed");

if(bytesReceived < 0)
{
    printf("Eroare la read.\n");
}


/* inchidem conexiunea, am terminat */
close (sd);

文件服务器发送：

 /*
 Welcome. Here you will resolve your problem. Please use <insert comand here> 
 to send back the file when you are done.

 Your task is to do <insert problem description here>.
 Time allocated: 20 minutes;

 May the force be with you.

 */

另外 recvBuff 有服务器发送的所有文本。预先感谢您对我的帮助。

编辑： 这是输出的图像。客户端在 fwrite 调用之前的 printf("Bytes received %d\n",bytesReceived); 之后卡住。 output

Answer 1

您忘记关闭服务器代码中的 client 描述符：您在子进程中分叉并关闭，但在父进程中没有，因此连接保持打开状态，客户端在其 read 用于永远不会出现的数据。那应该更正它（你的代码写得太糟糕了，看看是否还有其他错误）：

if(pid==0)
  {
    /* copil/client  */
    if (welcome(client))
      {
        sendTest(client);
        printf ("[server] S-a deconectat clientul cu descriptorul %d.\n",client);
            fflush (stdout);
        close (client);     /* inchidem conexiunea cu clientul */
        nr--;
        close(sd);
        exit(0);
      }
  } else // close the descriptor as parent is not in charge of managing the connection anymore
  {
    close(client);
  }

fwrite() 阻止调用并且不写入文件

fwrite() blocks call and doesn`t write to file

c

linux

tcp

fwrite