Question

为了尝试绕着udp套接字缠绕我，我试图将代码从本教程页面http://www.linuxhowtos.org/C_C++/socket.htm移植到winsock（如果重要的话，在win 8上运行）。 [以下直接链接]

代码当前编译并运行但我从未收到过数据包，两个程序只是等待并阻塞recvfrom（）。我一直有同样的问题（例如，此代码https://stackoverflow.com/a/679529/873217的修改版本包含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进行更改建议）。我想我正在犯一些简单而根本的错误;但是我无法独立找到它。希望有更多经验的人可以为我解决这个问题。谢谢。

附加说明：
我正在运行服务器exe，然后在同一台计算机上运行客户端exe。它连接到互联网。我也尝试过使用解析为我的IP地址的域名。我也试过禁用防火墙，虽然我已经允许两个程序完全访问。

指向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);
}

Answer 1

以下UDP测试应用程序在我的设置上正常运行 - Windows 7，VS 2013。

我创建了一些轻量级的包装类来进行资源管理，并将错误代码转换为异常。这使客户端和服务器代码更易于阅读。请务必先运行服务器。

<强> 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(); } }

<强>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; }

Answer 2

好吧，我不确定winsock2.h在Windows和Linux中的工作方式是否相同，但在Windows中，当您创建套接字时，必须设置您正在使用的协议，TCP或UDP： / p>

SOCKET sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

AF_INET = IPv4; SOCK_STREAM = TCP的字节流; IPPROTO_TCP = TCP协议。

对于UDP（我之前从未使用过），根据MSDN，它将是：

SOCKET sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

SOCK_DGRAM = UDP的字节流; IPPROTO_UDP = UDP协议。

该代码适用于Windows。我想在Linux中它会是类似的。

如何在c ++中使用winsock接收udp数据包？

2 个答案: