c++ - 通过 Winsock 发送键盘缓冲区

Question

现在我是 WINSOCK 的新手，对 C++ 不是很流利，所以请多多包涵。我编写了一个 NetworkServer 和 NetworkClient 类，主要基于 MSDN 教程。客户端将向服务器发送一个大小为 256 的字符数组，其中包含每个标准键盘按钮的状态(0 表示该键未被按下，1 表示它被按下)。

运行代码时，我首先启动服务器，然后是客户端。他们相互连接良好。然后调用客户端发送键盘缓冲区。发送缓冲区，但服务器挂起:

receiveResult = recv(theClient, buffer, sizeof(buffer), 0);

每个类中的“keys”变量是一个字符键[256]，用于保存每个键状态。

下面是网络服务器启动后发生的循环:

char buffer[256];
int receiveResult, sendResult;

// Receive from the client
do
{
    receiveResult = recv(theClient, buffer, sizeof(buffer), 0);
    if (receiveResult > 0 )
    {
        sendResult = send(theClient, buffer, receiveResult, 0);
        if (sendResult == SOCKET_ERROR)
        {
            sendResult = WSAGetLastError();
            JBS::reportSocketError(nret, "server send()");
            closesocket(theClient);
            WSACleanup();
            return;
        }
        else
        {
            memcpy(keys, buffer, sizeof(keys));
        }
    }

    else if (receiveResult == 0)
        cout << "Server closing." << endl;
    else
    {
        receiveResult = WSAGetLastError();
        JBS::reportSocketError(nret, "server receive()");
        closesocket(theClient);
        WSACleanup();
        return;
    }
} while (receiveResult > 0);

这里是 NetworkClient 发送方法:

char buffer[256];
memcpy(buffer, keys, sizeof(buffer));

nret = send(theSocket, buffer, sizeof(buffer),0);
if (nret == SOCKET_ERROR)
{
    nret = WSAGetLastError();
    JBS::reportSocketError(nret, "client send()");
    closesocket(theSocket);
    WSACleanup();
} 
do
{   
    char buff[256];
    nret = recv(theSocket, buff, sizeof(buff), 0);
    if (nret > 0)
    {
        memcpy(keys, buff, sizeof(keys));
    }
    else if (nret == 0)
        cout << "Server connection closed" << endl;
    else
    {
        nret = WSAGetLastError();
        JBS::reportSocketError(nret, "client receive()");
        closesocket(theSocket);
        WSACleanup();
    }

} while (nret > 0);

正如我所说，正在客户端和服务器之间建立连接，但进程的接收部分似乎无法正常工作。任何帮助将不胜感激。

NetworkClient的启动方法:

sockVersion = MAKEWORD(1, 1);

// Initialize Winsock as before
WSAStartup(sockVersion, &wsaData);

// Store information about the server
LPHOSTENT hostEntry;

hostEntry = gethostbyname(serverAddress);     // Specifying the server by its name;

if (!hostEntry) {
    nret = WSAGetLastError();
    JBS::reportSocketError(nret, "client gethostbyname()");         // Report the error as before
    closesocket(theSocket);
    WSACleanup();
}

// Create the socket
theSocket = socket(AF_INET,                      // Go over TCP/IP
    SOCK_STREAM,                  // This is a stream-oriented socket
    IPPROTO_TCP);                 // Use TCP rather than UDP

if (theSocket == INVALID_SOCKET) {
    nret = WSAGetLastError();
    JBS::reportSocketError(nret, "client socket()");
    closesocket(theSocket);
    WSACleanup();
}

// Fill a SOCKADDR_IN struct with address information
serverInfo.sin_family = AF_INET;
serverInfo.sin_addr = *((LPIN_ADDR)*hostEntry->h_addr_list);
serverInfo.sin_port = htons(PORT);              // Change to network-byte order and
                                                // insert into port field

// Connect to the server
nret = connect(theSocket, (LPSOCKADDR)&serverInfo, sizeof(struct sockaddr));

if (nret == SOCKET_ERROR) 
{
    nret = WSAGetLastError();
    JBS::reportSocketError(nret, "client connect()");
    closesocket(theSocket);
    WSACleanup();
}
// Successfully connected!
started = true;

Answer 1

在客户端代码中，您写道:

char buff[256];
nret = recv(theSocket, buff, (int)strlen(buff), 0);

这意味着您要将数据接收到长度为strlen(buff) 的缓冲区中。不幸的是，strlen() 返回缓冲区内 string 的长度，即缓冲区内任何 NUL 字符之前的数据长度。你的编译器足够聪明，用 NUL 字符初始化 buff，因此 strlen(buf) 返回 0，这意味着你想接收 0 字节的数据。因此，recv() 没有收到任何东西。

你的意思是:

nret = recv(theSocket, buff, sizeof(buff), 0);

(如果您尝试使用 Release 版本编译您的程序，它会很高兴地崩溃，因为 buff 将不会被初始化，并且 strlen()会返回一个相当随机的结果，这会导致程序访问无效的内存地址...)

我应该补充一点，你声明你的缓冲区的方式是不幸的:你有一个 bool 数组(值 1 或 0 取决于键的状态)。 bool 值不是字符。严格的声明应该是 bool buff[256]...