Question

我目前正在使用CentOS进行vm之间的实验。我想知道使用客户端和服务器套接字C编程的TCP交互。我有两个VM，其中包含＆＃39; vm_A＆＃39;和＆＃39; vm_B＆＃39;作为他们的主持人。

从vm_A我尝试使用ssh连接vm_B并且它已连接，并且相互ping通。但是，当我尝试在vm_A上运行./echoserver而在vm_B上运行./echoclient [ip vm_A]时，通过vm_A使用ssh远程访问。它一直在说连接服务器时出现问题：无主机路由＆＃39;

我尝试过使用主机名@ ip vm_A，但仍然会返回错误。

以下是echoserver.c的代码

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


#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
#define LISTENQ 8 /*maximum number of client connections*/

int main (int argc, char **argv)
{
 int listenfd, connfd, n;
 pid_t childpid;
 socklen_t clilen;
 char buf[MAXLINE];
 struct sockaddr_in cliaddr, servaddr;

 //Create a socket for the soclet
 //If sockfd<0 there was an error in the creation of the socket
 if ((listenfd = socket (AF_INET, SOCK_STREAM, 0)) <0) {
  perror("Problem in creating the socket");
  exit(2);
 }


 //preparation of the socket address
 servaddr.sin_family = AF_INET;
 servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
 servaddr.sin_port = htons(SERV_PORT);

 //bind the socket
 bind (listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));

 //listen to the socket by creating a connection queue, then wait for clients
 listen (listenfd, LISTENQ);

 printf("%s\n","Server running...waiting for connections.");

 for ( ; ; ) {

  clilen = sizeof(cliaddr);
  //accept a connection
  connfd = accept (listenfd, (struct sockaddr *) &cliaddr, &clilen);

  printf("%s\n","Received request...");

  if ( (childpid = fork ()) == 0 ) {//if it?s 0, it?s child process

    printf ("%s\n","Child created for dealing with client requests");

    //close listening socket
    close (listenfd);

    while ( (n = recv(connfd, buf, MAXLINE,0)) > 0)  {
     printf("%s","String received from and resent to the client:");
     puts(buf);
     send(connfd, buf, n, 0);
    }

    if (n < 0)
      printf("%s\n", "Read error");
    exit(0);
  }
  //close socket of the server
  close(connfd);
 }
}

以下是echoclient.c的代码

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


#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/

int
main(int argc, char **argv) 
{
 int sockfd;
 struct sockaddr_in servaddr;
 char sendline[MAXLINE], recvline[MAXLINE];

 //basic check of the arguments
 //additional checks can be inserted
 if (argc !=2) {
  perror("Usage: TCPClient <IP address of the server"); 
  exit(1);
 }

 //Create a socket for the client
 //If sockfd<0 there was an error in the creation of the socket
 if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) <0) {
  perror("Problem in creating the socket");
  exit(2);
 }

 //Creation of the socket
 memset(&servaddr, 0, sizeof(servaddr));
 servaddr.sin_family = AF_INET;
 servaddr.sin_addr.s_addr= inet_addr(argv[1]);
 servaddr.sin_port =  htons(SERV_PORT); //convert to big-endian order

 //Connection of the client to the socket 
 if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr))<0) {
  perror("Problem in connecting to the server");
  exit(3);
 }

 while (fgets(sendline, MAXLINE, stdin) != NULL) {

  send(sockfd, sendline, strlen(sendline), 0);

  if (recv(sockfd, recvline, MAXLINE,0) == 0){
   //error: server terminated prematurely
   perror("The server terminated prematurely"); 
   exit(4);
  }
  printf("%s", "String received from the server: ");
  fputs(recvline, stdout);
 }

 exit(0);
}

你对我有任何建议吗？先感谢您。

客户端无法访问服务器（VM到VM交互），Ping ok，SSH ok

0 个答案: