无法使用 getsockname() 打印出服务器套接字的特定地址

Question

我使用getpeername() 和getsockname() 在服务器端打印出客户端socket 和服务器socket 的IP 地址。但是，只指定了客户端套接字的IP地址，而服务器套接字的IP地址是0.0.0.0。我该如何解决这个问题，以便可以指定服务器套接字的 IP 地址？

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

 static const int MAXPENDING = 5; // Maximum outstanding connection requests

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

  if (argc != 2) // Test for correct number of arguments
    DieWithUserMessage("Parameter(s)", "<Server Port>");

  in_port_t servPort = atoi(argv[1]); // First arg: local port

 // Create socket for incoming connections
  int servSock; // Socket descriptor for server
 if ((servSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    DieWithSystemMessage("socket() failed");

 // Construct local address structure
 struct sockaddr_in servAddr; // Local address
 memset(&servAddr, 0, sizeof(servAddr)); // Zero out structure
 servAddr.sin_family = AF_INET; // IPv4 address family
 servAddr.sin_addr.s_addr = htonl(INADDR_ANY); // Any incoming interface
 servAddr.sin_port = htons(servPort); // Local port

 // Bind to the local address
 if (bind(servSock, (struct sockaddr*) &servAddr, sizeof(servAddr)) < 0)
    DieWithSystemMessage("bind() failed");

 // Mark the socket so it will listen for incoming connections
 if (listen(servSock, MAXPENDING) < 0)
    DieWithSystemMessage("listen() failed");

 for (;;) { // Run forever
    struct sockaddr_in clntAddr; // Client address
    // Set length of client address structure (in-out parameter)
    socklen_t clntAddrLen = sizeof(clntAddr);
    // Wait for a client to connect
    int clntSock = accept(servSock, (struct sockaddr *) &clntAddr, &clntAddrLen);
    if (clntSock < 0)
       DieWithSystemMessage("accept() failed"); 

   // clntSock is connected to a client!

   char clntName[INET_ADDRSTRLEN]; // String to contain client address
   if (inet_ntop(AF_INET, &clntAddr.sin_addr.s_addr, clntName, sizeof(clntName)) != NULL)
       printf("Handling client %s/%d\n", clntName, ntohs(clntAddr.sin_port));
   else
       puts("Unable to get client address");
   getpeername(servSock, (struct sockaddr *) &clntAddr, &clntAddrLen);
   inet_ntop(AF_INET, &clntAddr.sin_addr.s_addr, clntName, sizeof(clntName));
   printf("After accept(): The client IP address is: %s and client port is: %u \n", clntName, ntohs(clntAddr.sin_port));

   char serverIP[INET_ADDRSTRLEN];
   socklen_t servlen = sizeof(servAddr);
   inet_ntop(AF_INET, &servAddr.sin_addr, serverIP, sizeof(serverIP));
   getsockname(servSock, (struct sockaddr *) &servAddr, &servlen);
   printf("After accept(): The server IP address is %s and server port is %u \n", serverIP, servPort);

   HandleTCPClient(clntSock);
 }
 // NOT REACHED
}

输出是：

客户端socket的IP地址：10.0.2.15

服务器套接字的IP地址：0.0.0.0

那么，我怎样才能使服务器套接字的 IP 地址具体为 10.0.2.15 而不是 0.0.0.0

Answer 1

    int clntSock = accept(servSock, (struct sockaddr *) &clntAddr, &clntAddrLen);

   getpeername(servSock, (struct sockaddr *) &clntAddr, &clntAddrLen);

您必须使用clntSock 致电getpeername()。 getsockname() 同上。

当使用无效套接字调用时，这两个函数都可能失败（这可能发生在您的程序中）并返回随机数据。