send（）时套接字失去连接

Question

我想用C语言为我的世界建立一个假的播放器。

我的Minecraft服务器（bukkit）正在本地IP 192.168.1.141上的端口25565上侦听

当我启动应用程序时（当它通过套接字发送数据时），bukkit服务器会说：“192.168.1.141:XXXXX失去连接”，并且

socked created
socked connected
to send data = (smilie)kekos91;192.168.1.141:25565
to send length = 27
send !
response data = (a strange symbol)
response length = 1
socket disconnected

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <winsock2.h>

int main()
{
    char pseudo[] = "kekos91;192.168.1.141:25565";
    int pseudoLen = strlen(pseudo);
    
    char *packet = NULL;
    packet = (char*)malloc(3 + ((pseudoLen)*sizeof(char)*2));
    if(packet == NULL)
    {
        return -1;
    }
    memset(packet, '\0', sizeof(packet));
    packet[0] = (char)0x02;
    strcat(packet, pseudo);
    int pLenght = strlen(packet);
    
    char handshake[200];
    
    HANDLE hConsole;
    WSADATA wsaData;
    int iResult = 0;

    SOCKET serverSocket;
    sockaddr_in serverInfos;

    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        printf("WSAStartup() failed with error: %d\n", iResult);
        return -1;
    }

    serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (serverSocket == INVALID_SOCKET) {
        printf("socket function failed with error: %i\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }
    printf("socket created\n");

    serverInfos.sin_family = AF_INET;
    serverInfos.sin_addr.s_addr = inet_addr("192.168.1.141");
    serverInfos.sin_port = htons(25565);

    iResult = connect(serverSocket, (SOCKADDR *)&serverInfos, sizeof(serverInfos));
    if (iResult == SOCKET_ERROR)
    {
        printf("connect function failed with error: %i\n", WSAGetLastError());
        iResult = closesocket(serverSocket);
        if (iResult == SOCKET_ERROR)
        {
           printf("closesocket function failed with error: %i\n", WSAGetLastError());
        }
        WSACleanup();
        return -1;
    }
    printf("socket connected\n");
    
    
    
    printf("to send data = %s\n", packet);
    printf("to send length = %i\n", pseudoLen);
    Sleep(500); // after this point, the connection is loose :(
    if(send(serverSocket, (char*)packet , pLenght, 0) == SOCKET_ERROR)
    {
        printf("send function failed with error: %i\n", WSAGetLastError());
        iResult = closesocket(serverSocket);
        if (iResult == SOCKET_ERROR)
        {
           printf("closesocket function failed with error: %i\n", WSAGetLastError());
        }
        WSACleanup();
        return -1;
    }
    free(packet);
    
    printf("send !\n");
    
    
    
    
    if(recv(serverSocket, (char*)&handshake, 200, 0) == SOCKET_ERROR)
    {
        printf("recv function failed with error: %i\n", WSAGetLastError());
        iResult = closesocket(serverSocket);
        if (iResult == SOCKET_ERROR)
        {
           printf("closesocket function failed with error: %i\n", WSAGetLastError());
        }
        WSACleanup();
        return -1;
    }
    
    printf("response data = %s\n", handshake);      
    printf("response length = %i\n", strlen(handshake)); 
     
    iResult = closesocket(serverSocket);
    if (iResult == SOCKET_ERROR) {
        printf("closesocket function failed with error %i\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }
    printf("socket disconnected.\n");
    
    WSACleanup();
    Sleep(5000);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <winsock2.h>

int main()
{
    int iSocketResult = 0; // it will retrieve sockets return functions, like send / recv / errors
    
    wchar_t wcPseudo[] = L"kekos91;192.168.1.141:25565";
    int iPseudoLen = wcslen(wcPseudo);
    
    char *pPacket = NULL;
    pPacket = (char*)malloc(3 + ((iPseudoLen)*sizeof(char)*2));
    if(pPacket == NULL)
    {
        return -1;
    }
    pPacket[0] = 0x02;
    
    
    *(short*)( pPacket + 1 ) = htons( iPseudoLen );
    memcpy( pPacket + 3, wcPseudo, iPseudoLen * sizeof( wchar_t ));

    int iPacketLen = 3 + iPseudoLen*sizeof(wchar_t) ;    

    char *handshake  = NULL;
    handshake = (char*)malloc(sizeof(char)*200);
    if(handshake == NULL)
    {
        return -1;
    }
    
    
    HANDLE hConsole;
    WSADATA wsaData;        
    
    SOCKET serverSocket;
    sockaddr_in serverInfos;

    iSocketResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iSocketResult != NO_ERROR) {
        printf("WSAStartup() failed with error: %d\n", iSocketResult);
        return -1;
    }

    serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (serverSocket == INVALID_SOCKET) {
        printf("socket function failed with error: %i\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }
    
    printf("socket created\n");

    serverInfos.sin_family = AF_INET;
    serverInfos.sin_addr.s_addr = inet_addr("192.168.1.141");
    serverInfos.sin_port = htons(25565);

    iSocketResult = connect(serverSocket, (SOCKADDR *)&serverInfos, sizeof(serverInfos));
    if (iSocketResult == SOCKET_ERROR)
    {
        printf("connect function failed with error: %i\n", WSAGetLastError());
        iSocketResult = closesocket(serverSocket);
        if (iSocketResult == SOCKET_ERROR)
        {
           printf("closesocket function failed with error: %i\n", WSAGetLastError());
        }
        WSACleanup();
        return -1;
    }
    printf("socket connected\n\n");
    
    printf("to send protocol = %#1.2x \nlenght = %i\n", pPacket[0], iPseudoLen);
    
    iSocketResult = send(serverSocket, pPacket , iPacketLen, 0);
    if(iSocketResult == SOCKET_ERROR)
    {
        printf("send function failed with error: %i\n", WSAGetLastError());
        iSocketResult = closesocket(serverSocket);
        if (iSocketResult == SOCKET_ERROR)
        {
           printf("closesocket function failed with error: %i\n", WSAGetLastError());
        }
        WSACleanup();
        return -1;
    }
    free(pPacket);
    
    printf("send %i (bytes) !\n\n",iSocketResult);
    
    
    iSocketResult = recv(serverSocket, handshake, 50, 0);
    if( iSocketResult == SOCKET_ERROR)
    {
        printf("recv function failed with error: %i\n", WSAGetLastError());
        iSocketResult = closesocket(serverSocket);
        if (iSocketResult == SOCKET_ERROR)
        {
           printf("closesocket function failed with error: %i\n", WSAGetLastError());
        }
        WSACleanup();
        return -1;
    }
    
    printf("response protocol = %#1.2x\nresponse lenght = %i (bytes)\n\n", handshake[0], iSocketResult);
    free(handshake);    
    
    
    iSocketResult = closesocket(serverSocket);
    if (iSocketResult == SOCKET_ERROR)
    {
        printf("closesocket function failed with error %i\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }
    printf("socket disconnected.\n");
    
    WSACleanup();
    Sleep(7000);
    return 0;
}

输出控制台现在打印：

socket created
socket connected

to send protocol = 0x02 
lenght = 27
send 57 (bytes) !

response protocol = 0x02
response lenght = 37 (bytes)

socket disconnected.

感谢你们所有人！

Answer 1

总的来说，你所做的似乎是正确的。我可以想象，当测试代码关闭它自己的套接字时，来自服务器的“连接丢失”消息就会发生。但是，看起来您没有正确地处理字符串数据类型。字符串需要以Unicode的形式发送，而且您似乎是以单字节字符的形式发送的。此外，string前面还需要有表示为2字节整数的长度。

握手字符串可能应该用wchar_t（或您喜欢的宽字符数据类型）指定如下。并在文字上使用L来指定宽字符串。以字节为单位的实际发送长度需要确保字符串长度乘以2。

wchar_t pseudo[]=L“kekos91；192.168.1.141:25565”；int pseudoLen=wcslen（pseudo）；

*((short*)( packet + 1 ) = htons( pseudolLen );

memcpy( packet + 3, pseudo, pseudoLen * sizeof( wchar_t ));

在打印结果响应时，您可能需要以下内容：

printf( "Protocol response: %02x\n", handshake[0] );

然后提取字符串（协议字节后面的两个字节应该是连接哈希字符串的长度（按网络字节顺序）。所以您需要使用ntohs来提取它。然后下面的N个宽字符表示哈希。

写完所有这些之后，在我看来，您可能想要寻找一个库来处理所有的协议。我没有看过，但似乎有一些与Minecraft相关的C套接字库可用。只是胡乱猜测。再考虑一下，这取决于你的目标。如果您只是想尽可能快地构建客户机，那么寻找库肯定是有意义的。但是，如果您想学习协议、网络编程等的细节，那么按照您开始的级别编写它是一个好主意，而且会很有趣，因为您可以执行渐进的步骤，经常显示真正的结果。