Question

我正在使用C ++中的UDP套接字，它一次是客户端，也是服务器。我正在使用Visual Studio 2017并在Windows 7上运行它。我遇到了一些recvfrom（）函数的问题，即＃34;无效参数＆＃34;错误。我认为套接字是可以的，sockaddr_in结构是可以的，线程是可以的，甚至与sendto（）函数的while循环是可以的。但线程在调用recvfrom（）函数后结束，我真的不知道问题出在哪里......

#include <iostream>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <winsock2.h>
#include <thread>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

void printMessage(SOCKET s, SOCKADDR_IN destAddr) {

    char message[100];
    int result, error;
    int addrSize = sizeof(destAddr);
    do {
        printf("som v threade\n");
        result = recvfrom(s, message, 100, 0, (SOCKADDR*)&destAddr, &addrSize);
        printf("%d\n", result);

        if (result < 0) {
            error = WSAGetLastError();
            printf("%d\n", error);
        }

        if (result > 0)
            printf("%s", message);

    } while (result > 0);

}


int main(int argc, char *argv[]) {

    WORD dllVersion = MAKEWORD(2, 1);
    WSADATA wsaData;

    if (WSAStartup(dllVersion, &wsaData) != 0) {
        printf("Winsock startup failed");
        exit(1);
    }

    const char *ip = "127.0.0.1";
    int dstPort = 49999;
    int srcPort = 49999;

    SOCKADDR_IN destaddr, srcaddr;
    SOCKET s;
    s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

    if (s < 0) {
        printf("Error creating socket");
        exit(1);
    }

    destaddr.sin_family = AF_INET;
    destaddr.sin_addr.s_addr = inet_addr(ip);
    destaddr.sin_port = htons(dstPort);

    srcaddr.sin_family = AF_INET;
    srcaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    srcaddr.sin_port = htons(srcPort);


    bind(s, (SOCKADDR*)&srcaddr, sizeof(srcaddr));

    thread receiving (printMessage, s, destaddr);
    receiving.detach();

    while (1) {
        char message[100];

        printf("Write a message:");
        scanf("%s", message);

        if (sendto(s, message, sizeof(message), 0, (SOCKADDR *) &destaddr, sizeof(destaddr)) < 0) {
            printf("Message not sent");
            exit(1);
        }
    }
    return 0;
}

Answer 1

错误代码10022是WSAEINVAL。根据{{3}}文档：

WSAEINVAL

套接字尚未与bind() 绑定，或者指定了未知标志，或者为启用了MSG_OOB的套接字指定了SO_OOBINLINE，或者（仅适用于字节流式套接字）len为零或负数。

您没有进行任何错误处理，以确保您的bind()来电没有失败。或者甚至您正在调用正确的bind()函数。 WinSock和STL都有自己的bind()函数，但是你的recvfrom()。

此外，每次调用addrSize时都需要重置recvfrom()，因为它可能会修改该值。它希望您传入最大缓冲区大小，然后输出实际写入缓冲区的大小。

此外，您没有在合适的时间致电WSAGetLastError()。在执行任何其他操作之前，您需要在WinSock调用失败后立即将其称为。换句话说，在调用printf()之前不要调用WSAGetLastError()，因为它可能会重置错误代码。

此外，如果recvfrom()成功读取，则假设数据为空终止，但不保证。您需要将result作为参数传递给printf()。

而且，你真的不应该将C风格的I / O与C ++混合使用。请改用C ++样式的I / O.

尝试更像这样的事情：

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

#pragma comment(lib, "Ws2_32.lib")

void printMessage(SOCKET s)
{
    char message[100];
    int result, error, addrSize;
    SOCKADDR_IN clientaddr;

    do {
        std::cout << "som v threade" << std::endl;
        addrSize = sizeof(clientaddr);
        result = recvfrom(s, message, 100, 0, (SOCKADDR*)&clientaddr, &addrSize);
        if (result == SOCKET_ERROR) {
            error = WSAGetLastError();
            std::cout << "Receive failed. Error: " << error << std::endl;
            continue;
        }
        std::cout << "Received " << result << " byte(s) from " << inet_ntoa(clientaddr.sin_addr) << ":" << ntohs(clientaddr.sin_port) << std::endl;
        if (result > 0) {
            std::cout.write(message, result);
            std::cout << std::endl;
        }
    }
    while (result > 0);
}

int main(int argc, char *argv[]) {
    WORD dllVersion = MAKEWORD(2, 1);
    WSADATA wsaData;    
    int result, error;

    result  = WSAStartup(dllVersion, &wsaData);
    if (result != 0) {
        std::cout << "Winsock startup failed. Error: " << result << std::endl;
        exit(1);
    }

    SOCKET s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (s == INVALID_SOCKET) {
        error = WSAGetLastError();
        std::cout << "Socket creation failed. Error: " << error << std::endl;
        exit(1);
    }

    const char *ip = "127.0.0.1";
    unsigned short dstPort = 49999;
    unsigned short srcPort = 49999;

    SOCKADDR_IN destaddr = {};
    SOCKADDR_IN srcaddr = {};

    destaddr.sin_family = AF_INET;
    destaddr.sin_addr.s_addr = inet_addr(ip);
    destaddr.sin_port = htons(dstPort);

    srcaddr.sin_family = AF_INET;
    srcaddr.sin_addr.s_addr = INADDR_ANY;
    srcaddr.sin_port = htons(srcPort);

    result = ::bind(s, (SOCKADDR*)&srcaddr, sizeof(srcaddr));
    if (result == SOCKET_ERROR) {
        error = WSAGetLastError();
        std::cout << "Socket bind failed. Error: " << error << std::endl;
        exit(1);
    }

    std::thread receiving(printMessage, s);
    receiving.detach();

    std::string message;
    do {
        std::cout << "Write a message: ";
        std::getline(std::cin, message);
        result = sendto(s, message.c_str(), message.size(), 0, (SOCKADDR *) &destaddr, sizeof(destaddr));
        if (result == SOCKET_ERROR) {
            error = WSAGetLastError();
            std::cout << "Message not sent. Error: " << error << std::endl;
            exit(1);
        }
    }
    while (true);

    return 0;
}

Answer 2

包含类似文件后，我也遇到了同样的问题

#include <thread> /*or*/ #include <future>

原来是bind()和std::bind()之间的混淆。

删除using namespace std;或直接使用::bind()。

winsock2：recvfrom（）函数以错误10022结尾（无效参数）

2 个答案: