c - 为 winsock recvfrom 设置超时

Question

我正在尝试设置一个阻塞套接字，使其在尝试在端口上接收 recvfrom() 16 毫秒后超时。平台是Windows。我在网上看了很多例子，看起来真的很简单，但我似乎无法让它发挥作用。任何帮助将不胜感激!

#include <winsock2.h>
#include <string>

#pragma comment(lib, "ws2_32.lib")

#define PORT_NUM 8001

int main(void)
{
  std::string localIP;
  sockaddr_in localAddr;
  sockaddr_in remoteAddr;
  hostent* localhost;
  char buffer[1024];
  WSADATA wsData;

  int result = WSAStartup(MAKEWORD(2,2), &wsData);  // winsock version 2

  localhost = gethostbyname("");
  localIP   = inet_ntoa(*(in_addr*)*localhost->h_addr_list);

  localAddr.sin_family       = AF_INET;
  localAddr.sin_port         = htons(PORT_NUM);             // Set Port Number
  localAddr.sin_addr.s_addr  = inet_addr(localIP.c_str());  // Set IP Address

  int mHandle = WSASocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP, NULL, 0, 0);

  if(mHandle == INVALID_SOCKET)
    return 1;


  if(bind(mHandle, (SOCKADDR*)&localAddr, sizeof(localAddr)) == SOCKET_ERROR)
    return 1;

  timeval tv;
  tv.tv_sec  = 0;
  tv.tv_usec = 1600;

    // Set Timeout for recv call
  if(setsockopt(mHandle, SOL_SOCKET, SO_RCVTIMEO, 
                reinterpret_cast<char*>(&tv), sizeof(timeval)))
    return 1;

  int length = sizeof(remoteAddr);

  // <-- Blocks here forever
  recvfrom(mHandle, buffer, 1024, 0, (SOCKADDR*)&remoteAddr, &length);  

  return 0;
}

/*  I've also tried passing the time like so:
int ms = 16;

if(setsockopt(mHandle, SOL_SOCKET, SO_RCVTIMEO, reinterpret_cast<char*>(&ms), sizeof(int)))
  return 1; */

Answer 1

我查看了 select 函数，正如 laura 所说我应该做的那样，并且让它真正轻松地工作!谢谢!

fd_set fds ;
int n ;
struct timeval tv ;

// Set up the file descriptor set.
FD_ZERO(&fds) ;
FD_SET(mHandle, &fds) ;

// Set up the struct timeval for the timeout.
tv.tv_sec = 10 ;
tv.tv_usec = 0 ;

// Wait until timeout or data received.
n = select ( mHandle, &fds, NULL, NULL, &tv ) ;
if ( n == 0)
{ 
  printf("Timeout..\n");
  return 0 ;
}
else if( n == -1 )
{
  printf("Error..\n");
  return 1;   
}

int length = sizeof(remoteAddr);

recvfrom(mHandle, buffer, 1024, 0, (SOCKADDR*)&remoteAddr, &length);