无法关闭服务器端套接字

Question

以下是单个服务器-客户端代码，它尝试发送-接收少量缓冲区，然后关闭连接。 服务器代码：

#include <stdio.h>
#include <stdlib.h>     
#include <string.h>
#include <string>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/telnet.h>
#include <unistd.h>

char buff1[][3]= {{0xff , 0xfd, 0x18},{0xff , 0xfd, 0x1e},{0xff , 0xfd, 0x1d}};

char recbuf[1024];

void mwrite (int sock, char * buf, int size)
{
    int n = send( sock, buf, size, 0 );
    if (n < 0) 
    {
         perror("ERROR writing to socket");
         return;
    }

}


void read (int sock)
{
    char buffer[256];

    /* Now read client response */
    memset(buffer, 0, sizeof(buffer));
    int n = recv( sock, buffer, 255, 0 );
    if (n < 0) 
    {
         perror("ERROR reading from socket");
         return;
    }
    for (int i = 0; i < n; i++)
         printf("%2x ", buffer[i]);//printing ascii characters
    printf("\n");
}

int main(int argc , char *argv[] )
{
  int sockfd , newsockfd , portno;
  socklen_t clilen;
  char buffer[256];
  struct sockaddr_in serv_addr, cli_addr;
  int n;

  sockfd = socket(AF_INET , SOCK_STREAM , 0);
  if (sockfd < 0 )
  {
   perror("Error opening socket ");
   exit(1);
  }

  /* Initialize socket structure */
  bzero((char *) &serv_addr , sizeof(serv_addr));
  portno = atoi(argv[1]);
  serv_addr.sin_family = AF_INET;
  serv_addr.sin_addr.s_addr = INADDR_ANY ; 
  serv_addr.sin_port = htons(portno);

 /* Now bind the host address using client */
  if(bind(sockfd, (struct sockaddr *) &serv_addr , sizeof(serv_addr)) <0)

  { 
   perror("Error on binding");
   exit(1);
  } 
        if(listen(sockfd,5)<0)
     {
       perror("Error on listen");
       exit(1);
     }
       int count = 1;
       clilen = sizeof(cli_addr);
    newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr, &clilen);

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

         printf("Server Sending (DO TERMINAL TYPE)\n");
         while ((n = write(newsockfd,buff1,sizeof(buff1)))>0)
         {
           printf("Server Sent query %d: %x %x %x\n", count, buff1[count][0], buff1[count][1],    buff1[count][2]);
           n = read(newsockfd, recbuf , sizeof(recbuf));
           printf("Server received responset: %x %x %x\n", recbuf[0], recbuf[1], recbuf[2]);
           count++;
           count = count % 3;
           if(n<0)
            {
             perror("Error writing to socket ");
             exit(1);
            }

        }   
   return 0 ; 
}

客户代码：

#include <stdio.h>
#include <stdlib.h>     
#include <string.h>
#include <string>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/telnet.h>
#include <unistd.h>
#include <netdb.h>

char buff2[] = {0xff,0xfc,0x18};

void read (int sock)
{
    char buffer[256];

    /* Now read server response */
    memset(buffer, 0, sizeof(buffer));
    int n = recv( sock, buffer, 255, 0 );
    if (n < 0) 
    {
         perror("ERROR reading from socket");
         return;
    }
    printf("\n%d bytes received buffer is: %s", n, buffer);

}

void mwrite (int sock, char * buf, int size)
{
    int n = send( sock, buf, size, 0 );
    if (n < 0) 
    {
         perror("ERROR writing to socket");
         return;
    }
    printf("Bytes Sent: %d\n", n);
  }


int main(int argc, char *argv[])
 {
    int sockfd, portno, n;
    struct sockaddr_in serv_addr;
    struct hostent *server1;

   char buffer1[256];

   if (argc < 3)
    {
        fprintf(stderr,"usage %s hostname port\n", argv[0]);
        return(0);
    }
    portno = atoi(argv[2]);
    /* Create a socket point */
    sockfd = socket(AF_INET, SOCK_STREAM, 0);

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

    server1 = gethostbyname(argv[1]);
    if (server1 == 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 *)server1->h_addr, (char*)&serv_addr.sin_addr.s_addr, server1->h_length);
    serv_addr.sin_port = htons( portno );


/*Connect to server*/
 if (connect( sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr) ) < 0) 
    {
         perror("ERROR connecting");
         return(1);
    }   
   printf("Recieving Buffer 1 from Server side"); 
    bzero(buffer1,256);
    while(true)
    {
    n= read(sockfd,buffer1,sizeof(buffer1));
    if(n<0)
    printf("ERROR reading in socket %d  len %d", n, sizeof(buffer1));

    n= write(sockfd,buff2,sizeof(buff2));
    if(n<0)
    printf("ERROR writing in socket %d  len %d", n, sizeof(buff2));
    printf("\nSent Buffer2 (WON'T TERMINAL TYPE) from client side");
    }
return 0;
}

输出： 服务器端：

./single_sample 5667
Server Sending (DO TERMINAL TYPE)
Server Sent query 1: ffffffff fffffffd 1e
Server received responset: ffffffff fffffffc 18
Server Sent query 2: ffffffff fffffffd 1d
Server received responset: ffffffff fffffffc 18
Error writing to socket : Connection reset by peer

客户端：

./sample_client 127.0.0.1 5667
Recieving Buffer 1 from Server side
Sent Buffer2 (WON'T TERMINAL TYPE) from client side

基本上，一旦发送了两个缓冲区，我就会尝试关闭套接字。但得到上述错误。我无法解决错误是从服务器端还是客户端发生的。 此外，在 linux 机器上运行此代码时，如何捕获在 wireshark 上发送的数据字节 提前致谢。

Answer 1

您的客户端写入其消息，然后立即断开连接，这导致服务器收到Connection reset by peer 错误 - 因为连接的客户端部分不再存在。