作为对 udp 套接字进行深入研究的尝试，我尝试从本教程页面移植代码 http://www.linuxhowtos.org/C_C++/socket.htm到 winsock(如果重要的话，在 win 8 上运行)。 [下面的直接链接]
代码目前可以编译和运行，但我从未收到数据包，两个程序只是等待并阻塞在 recvfrom() 上。我一直遇到同样的问题(例如，此代码的修改版本 https://stackoverflow.com/a/679529/873217 包括 recvfrom() 调用。并使用此代码 C++ problem with Datagram (UDP)winsocket to sendto and recvfrom on the same socket through the loopback adapter 进行建议的更改)。我想我正在犯一些简单而根本的错误；但我无法自己找到它。希望有更多经验的人可以为我阐明这个问题。谢谢。
补充说明:
我在同一台计算机上运行服务器 exe，然后运行客户端 exe。它已连接到互联网。我也尝试过使用解析为我的 IP 地址的域。我也尝试过禁用防火墙，尽管我已经允许这两个程序完全访问。
原始客户端和服务器代码的直接链接:
http://www.linuxhowtos.org/data/6/client_udp.c
http://www.linuxhowtos.org/data/6/server_udp.c
我目前的尝试:
都链接到 libws2_32.a
客户端代码:
#include <stdio.h>
#include <winsock2.h>
#include <string.h>
void error(const char *);
int main()
{
WSAData data;
WSAStartup( MAKEWORD( 2, 2 ), &data );
int sock, n;
int length;
struct sockaddr_in server, from;
struct hostent *hp;
char buffer[256];
unsigned short serverPort = 27072;
sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) error("socket");
server.sin_family = AF_INET;
hp = gethostbyname("localhost");//have also tried my url
if (hp==0) error("Unknown host");
memmove((char *)hp->h_addr, (char *)&server.sin_addr, hp->h_length);
server.sin_port = htons(serverPort);
length = sizeof(struct sockaddr_in);
printf("Please enter the message: ");
memset(buffer, 0, 256);
fgets(buffer, 255, stdin);
n = sendto (sock, buffer, strlen(buffer), 0, (const struct sockaddr *)&server, length);
if (n < 0) error("Sendto");
printf("sent %i bytes\n", n);
n = recvfrom(sock, buffer, 256, 0, (struct sockaddr *)&server, &length);
if (n < 0) error("recvfrom");
//write(1,"Got an ack: ", 12);
//write(1, buffer, n);
printf("Got msg: %s\n",buffer);
closesocket(sock);
WSACleanup();
return(0);
}
void error(const char *msg)
{
perror(msg);
exit(0);
}
服务器代码:
#include <stdio.h>
#include <winsock2.h>
#include <string.h>
void error(const char *);
int main()
{
WSAData data;
WSAStartup( MAKEWORD( 2, 2 ), &data );
int sock, length, n;
int fromlen;
struct sockaddr_in server;
struct sockaddr_in from;
char buf[1024];
unsigned short serverPort = 27072;
sock=socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) error("Opening socket");
length = sizeof(server);
memset(&server, 0, length);
server.sin_family = AF_INET;
server.sin_addr.s_addr=INADDR_ANY;
server.sin_port=htons(serverPort);
if (bind(sock,(struct sockaddr *)&server, length)<0) error ("binding");
fromlen = sizeof(struct sockaddr_in);
while(1)
{
n = recvfrom(sock, buf, 1024, 0, (struct sockaddr *)&from, &fromlen);
if (n<0) error("recvfrom");
//write(1,"Received a datagram: ", 21);
//write(1,buf,n);
printf("Received a datagram: %s", buf);
n = sendto(sock, "Got your message\n",17,0,(struct sockaddr *)&from,fromlen);
if (n<0)error("sendto");
}
closesocket(sock);
WSACleanup();
return 0;
}
void error (const char *msg)
{
perror(msg);
exit(0);
}
最佳答案
以下 UDP 测试应用程序在我的设置上正常工作 - Windows 7、VS 2013。
我创建了一些轻量级的包装类来进行资源管理，并将错误代码转化为异常。这使得客户端和服务器代码更易于阅读。请务必先运行服务器。
Network.h
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <system_error>
#include <string>
#include <iostream>
#pragma once
class WSASession
{
public:
WSASession()
{
int ret = WSAStartup(MAKEWORD(2, 2), &data);
if (ret != 0)
throw std::system_error(WSAGetLastError(), std::system_category(), "WSAStartup Failed");
}
~WSASession()
{
WSACleanup();
}
private:
WSAData data;
};
class UDPSocket
{
public:
UDPSocket()
{
sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (sock == INVALID_SOCKET)
throw std::system_error(WSAGetLastError(), std::system_category(), "Error opening socket");
}
~UDPSocket()
{
closesocket(sock);
}
void SendTo(const std::string& address, unsigned short port, const char* buffer, int len, int flags = 0)
{
sockaddr_in add;
add.sin_family = AF_INET;
add.sin_addr.s_addr = inet_addr(address.c_str());
add.sin_port = htons(port);
int ret = sendto(sock, buffer, len, flags, reinterpret_cast<SOCKADDR *>(&add), sizeof(add));
if (ret < 0)
throw std::system_error(WSAGetLastError(), std::system_category(), "sendto failed");
}
void SendTo(sockaddr_in& address, const char* buffer, int len, int flags = 0)
{
int ret = sendto(sock, buffer, len, flags, reinterpret_cast<SOCKADDR *>(&address), sizeof(address));
if (ret < 0)
throw std::system_error(WSAGetLastError(), std::system_category(), "sendto failed");
}
sockaddr_in RecvFrom(char* buffer, int len, int flags = 0)
{
sockaddr_in from;
int size = sizeof(from);
int ret = recvfrom(sock, buffer, len, flags, reinterpret_cast<SOCKADDR *>(&from), &size);
if (ret < 0)
throw std::system_error(WSAGetLastError(), std::system_category(), "recvfrom failed");
// make the buffer zero terminated
buffer[ret] = 0;
return from;
}
void Bind(unsigned short port)
{
sockaddr_in add;
add.sin_family = AF_INET;
add.sin_addr.s_addr = htonl(INADDR_ANY);
add.sin_port = htons(port);
int ret = bind(sock, reinterpret_cast<SOCKADDR *>(&add), sizeof(add));
if (ret < 0)
throw std::system_error(WSAGetLastError(), std::system_category(), "Bind failed");
}
private:
SOCKET sock;
};
服务器
#include "Network.h"
int main()
{
try
{
WSASession Session;
UDPSocket Socket;
char buffer[100];
Socket.Bind(100);
while (1)
{
sockaddr_in add = Socket.RecvFrom(buffer, sizeof(buffer));
std::string input(buffer);
std::reverse(std::begin(input), std::end(input));
Socket.SendTo(add, input.c_str(), input.size());
}
}
catch (std::system_error& e)
{
std::cout << e.what();
}
}
客户端
#include "Network.h"
int main()
{
try
{
WSASession Session;
UDPSocket Socket;
std::string data = "hello world";
char buffer[100];
Socket.SendTo("127.0.0.1", 100, data.c_str(), data.size());
Socket.RecvFrom(buffer, 100);
std::cout << buffer;
}
catch (std::exception &ex)
{
std::cout << ex.what();
}
char c;
std::cin >> c;
}
关于c++ - 如何在 C++ 中使用 winsock 接收 udp 数据包？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14665543/