[英]UDP winsock server c++
我正在使用UDP连接进行一些套接字编程。 我已经编写了服务器(它也需要NTP服务器的偏移量),但是当我进行单元测试时,它在recvfrom函数中失败。 我是Winsock编程和网络编程的新手,所以我不确定从那里开始到底是什么。 这是我的代码:
NtpServer::NtpServer(u_short portnum, const std::chrono::nanoseconds desiredOffset) : portnum(0), client_length(0), bytes_received(0), current_time(0), desiredOffset(0)
{
WORD wVersionRequested;
wVersionRequested = MAKEWORD(2, 2);
WSADATA wsaData;
int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (WSAStartup(wVersionRequested, &wsaData) != 0)
{
std::cerr << "Could not open Windows connection" << std::endl;
exit(0);
}
sd = socket(AF_INET, SOCK_DGRAM, 0);
if (sd == INVALID_SOCKET)
{
std::cerr << "Could not create socket." << std::endl;
WSACleanup();
exit(0);
}
//blocking enabled
u_long iMode = 0;
iResult = ioctlsocket(sd, FIONBIO, &iMode);
if (iResult != NO_ERROR)
std::cerr << "ioctlsocket failed with error: " << iResult << std::endl;
memset((void *)&server, '\0', sizeof(struct sockaddr_in));
server.sin_family = AF_INET;
server.sin_addr.s_addr = htonl(INADDR_ANY);
server.sin_port = htons(portnum);
if (bind(sd, reinterpret_cast<SOCKADDR *>(&server),
sizeof(server)) == -1)
{
std::cerr << "Could not bind name to socket" << std::endl;
closesocket(sd);
WSACleanup();
exit(0);
}
getResult(desiredOffset);
}
和getResult函数:
void NtpServer::getResult(const std::chrono::nanoseconds desiredOffset)
{
ntp_data ntpData = ntp_data();
//struct for timeout
struct timeval tv;
tv.tv_sec = 10; // 10 Secs Timeout
setsockopt(sd, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv, sizeof(struct timeval));
while (1)
{
client_length = (int)sizeof(struct sockaddr_in);
/* Receive bytes from client */
bytes_received = recvfrom(sd, sendBuffer, NTP_PACKET_MAX, 0, (struct sockaddr *)&client, &client_length);
if (bytes_received < NTP_PACKET_MIN)
{
std::cerr << "Could not receive datagram." << std::endl;
closesocket(sd);
WSACleanup();
exit(0);
}
/* Check for time request */
if (strcmp(readBuffer, "GET TIME\r\n") == 0)
{
/* Get current time */
system_clock::time_point now = std::chrono::system_clock::now();
auto timepointoffset = (now + desiredOffset).time_since_epoch();
double current_value = std::chrono::duration_cast<std::chrono::duration<double>>(timepointoffset).count();
unpack_ntp(&ntpData, (unsigned char*)readBuffer, bytes_received);
make_packet(&ntpData, NTP_CLIENT, current_value);
pack_ntp((unsigned char *)sendBuffer, NTP_PACKET_MIN, &ntpData);
/* Send data back */
if (sendto(sd, sendBuffer,
(int)sizeof(sendBuffer), 0,
(struct sockaddr *)&client, client_length) !=
(int)sizeof(current_time))
{
std::cerr << "Error sending datagram." << std::endl;
closesocket(sd);
WSACleanup();
exit(0);
}
}
}
closesocket(sd);
WSACleanup();
}
您必须测试来自recvfrom()
错误-您正在设置SO_RCVTIMEO,因此可以预期接收会超时。
您是否真的要启用读取超时? 如果是这样,则在设置tv.tv_usec = 0
时,设置tv.tv_usec = 0
。 您没有对其进行初始化。 如果tv_usec恰好是一个无效值(小于0或大于999,999),则setsockopt()
调用将失败。
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