如何从“sockaddr_storage”实例中检索 IP 和端口？

Question

如何使用 getnameinfo() (ref) 从 sockaddr_storage 实例检索 IP 和端口？

当我使用 inet_ntop 时，它正常工作，但是当我将其替换为 getnameinfo 函数时，Windows 返回错误：

Code 10047: An address incompatible with the requested protocol was used.

#ifdef USE_IPV6
int fd = socket(AF_INET6, SOCK_DGRAM, 0);
#else
int fd = socket(AF_INET, SOCK_DGRAM, 0);
#endif

sockaddr_storage address;
int length = sizeof address;

char buffer[1];
recvfrom(fd, buffer, sizeof buffer, 0, (struct sockaddr *) &address, &length);

// Error
char ip[NI_MAXHOST];
char port[NI_MAXSERV];
int rc = getnameinfo((struct sockaddr *) &address, length, ip, sizeof ip, port, sizeof port, NI_NUMERICHOST | NI_NUMERICSERV);
if (rc) WSAGetLastError(); // Error Code = 10047

// Works
#ifdef USE_IPV6
struct sockaddr_in6 *sa = (struct sockaddr_in6 *) &address;
inet_ntop(AF_INET6, &sa->sin6_addr, ip, INET6_ADDRSTRLEN);
uint16_t port_ = ntohs(sa->sin6_port);
#else
struct sockaddr_in *sa = (struct sockaddr_in *) &address;
inet_ntop(AF_INET, &sa->sin_addr, ip, INET_ADDRSTRLEN);
uint16_t port_ = ntohs(sa->sin_port);
#endif

Answer 1

我查看了您的问题并重现了您遇到的错误。

可重现的例子：

#define WIN32_LEAN_AND_MEAN
#define _WINSOCK_DEPRECATED_NO_WARNINGS

#include <cstdint>
#include <cstdlib>
#include <iostream>
#include <windows.h>
#include <WinSock2.h>
#include <WS2tcpip.h>

int main(int, char **) {

  WORD wVersionRequested = MAKEWORD(2, 2);
  WSADATA wsaData;
  WSAStartup(wVersionRequested, &wsaData);

#ifdef USE_IPV6
  int fd = socket(AF_INET6, SOCK_DGRAM, 0);
#else
  SOCKET fd = socket(AF_INET, SOCK_DGRAM, 0);
#endif

  sockaddr_storage address;
  int length = sizeof(sockaddr_storage);

  char buffer[1];
  recvfrom(fd, buffer, sizeof buffer, 0, (struct sockaddr*)&address, &length);

  // Error
  char ip[NI_MAXHOST];
  char port[NI_MAXSERV];
  int rc = getnameinfo((struct sockaddr*)&address,
                       length,
                       ip,
                       sizeof(ip),
                       port,
                       sizeof(port),
                       NI_NUMERICHOST | NI_NUMERICSERV);
  if (rc)
    WSAGetLastError(); // Error Code = 10047

  std::cout << "IP: " << ip << std::endl;
  std::cout << "Port: " << port << std::endl;

// Works
#ifdef USE_IPV6
  struct sockaddr_in6* sa = (struct sockaddr_in6*)&address;
  inet_ntop(AF_INET6, &sa->sin6_addr, ip, INET6_ADDRSTRLEN);
  uint16_t port_ = ntohs(sa->sin6_port);
#else
  struct sockaddr_in* sa = (struct sockaddr_in*)&address;
  inet_ntop(AF_INET, &sa->sin_addr, ip, INET_ADDRSTRLEN);
  uint16_t port_ = ntohs(sa->sin_port);
#endif
}

问题在于您没有设置 sockaddr_storage 结构的 ss_family 字段。

要解决此问题，您需要在 sockaddr_storage 中指定 ss_family 值，如下所示：

sockaddr_storage address;
address.ss_family = AF_INET;

执行此操作后，您应该不会再看到错误 10047，您应该能够打印 ip 和端口缓冲区的内容并查看相应的信息。

参考文献：

如何从“sockaddr_storage”实例中检索 IP 和端口？

How to retrieve IP and port from a `sockaddr_storage` instance?

c++

c

sockets

networking

winsock