尝试从服务器 tcp 读回时客户端挂起

Question

我正在尝试创建一个简单的 TCP 服务器-客户端。如果客户端向服务器发送数据，但当服务器尝试回复时，我的程序工作正常，整个连接挂起。我正在使用 write()/read() 函数。

服务器代码：

#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <netinet/in.h>
#include <string.h>
#include <stdbool.h>

#define SIZE 700000000


///////////////////////////////////////////////////////////////////////////


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


  int sockfd, newsockfd, portno, clilen;
  char buffer[256];
  struct sockaddr_in serv_addr, cli_addr;
  int  n;


  /* First call to socket() function */
  sockfd = socket(AF_INET, SOCK_STREAM, 0);

  if (sockfd < 0) {
    perror("ERROR opening socket");
    exit(1);
  }

  bzero((char *) &serv_addr, sizeof(serv_addr));
  portno = 5001;

  serv_addr.sin_family = AF_INET;
  serv_addr.sin_addr.s_addr = INADDR_ANY;
  serv_addr.sin_port = htons(portno);



  if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
    perror("ERROR on binding");
    exit(1);
  }

  listen(sockfd, 10);
  clilen = sizeof(cli_addr);

  /* Accept actual connection from the client */
  newsockfd = accept(sockfd, (struct sockaddr *)&cli_addr, &clilen);

  if (newsockfd < 0) {
    perror("ERROR on accept");
    exit(1);
  }


  bzero(buffer, 255);

  int readbyte = 0;

  do {

    readbyte = read(newsockfd, buffer, 1024);

    if (readbyte < 0)
    {
      perror("ERROR on reading socket!");
      break;
    }
    if (readbyte > 0)
    {
      //printf("Here is the message: %s\n",buffer);
    }


  } while (readbyte > 0); /* until EOF */



  int writen = write(newsockfd, "I received your message", strlen("I received your message") + 1);

   if (writen<0){
    perror("Error");
   }

   //debug();

  return 0;
}

客户代码：

#include <stdio.h>
#include <stdlib.h>

#include <netdb.h>
#include <netinet/in.h>

#include <string.h>

//////////////////////////////////////////////////////////////////


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

  int sockfd, portno, n;
  struct sockaddr_in serv_addr;
  struct hostent *server;
  int mode;
  char *code;
  char buffer[256];
  char *uptr = buffer;
  int i;




  if (argc < 3) {
    fprintf(stderr, "Use:  %s [hostname] [port] [args]\n", argv[1]);
    exit(0);
  }

  portno = atoi(argv[2]);


  /* Create a socket point */
  sockfd = socket(AF_INET, SOCK_STREAM, 0);

  if (sockfd < 0) {
    perror("ERROR opening socket");
    exit(1);
  }

  server = gethostbyname(argv[1]);

  if (server == NULL) {
    fprintf(stderr, "ERROR, no such host\n");
    exit(0);
  }

  bzero((char *) &serv_addr, sizeof(serv_addr));
  serv_addr.sin_family = AF_INET;
  bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length);
  serv_addr.sin_port = htons(portno);

  int sock_et = connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr);

  /* Now connect to the server */
  if (sock_et < 0) {
    perror("ERROR connecting");
    exit(1);
  }
 /* some code... */

while (len > 0) {

    int writen = write(sockfd, buf, len + 1);

    if (writen < 0)
    {
      printf("Error writting to socket!\n");
      break;
    }

    len -= writen;
    buf += writen; /* tricky pointer arythmetic */

  }

 printf("Finished writing to server\n");
  bzero(buffer, 256);
  int readbyte;

 do {

     readbyte = read(sock_et, buffer, 1024);

    if (readbyte < 0)
    {
      perror("ERROR on reading socket!");
      break;
    }
    if (readbyte > 0)
    {
      //printf("Here is the message: %s\n",buffer);
    }


  } while (readbyte > 0); /* until EOF */

    printf("%s\n",buffer );




  close(sockfd);


  return 0;
}

如有任何帮助，我们将不胜感激！谢谢！

Answer 1

您的客户端代码无法编译
当套接字打开时（在客户端或服务器中），您永远不会从读取中获得 0（EOF）——所以现在只需在成功读取后添加一个 break。
您没有关闭服务器中的套接字
在客户端中，您需要从sockfd读取，而不是sock_et

可能还有其他问题。看起来你正在尝试使用 client.c/server.c 来自这里：http://www.linuxhowtos.org/C_C++/socket.htm

如果我使用这些文件，它工作正常。因此，从头开始并更仔细地应用您的更改。

尝试从服务器 tcp 读回时客户端挂起

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