c++ - 无法使用udp协议(protocol)从网络接收数据

我的目的是编写用UDP协议从网络接收数据的C++程序。操作系统-linux。我没什么问题。
我想确保我可以使用Linux C库来编写C++程序。
在任何地方都有一个完整的教程，一步一步地介绍如何在Linux中使用套接字编程吗？（我知道在网络上有很多教程，但我正在寻找一些东西来帮助我从INTERNET接收udp数据，而不是从同一设备上的另一个程序。）。
我在终端（使用tcpdump）中看到我的计算机接收到指向指定端口的udp包。我的程序有什么问题

class Connection
{
private:
    char * buffer;
    int bufferSize;
    int sock;
    struct sockaddr_in server;
    struct sockaddr_in other;
    socklen_t addressLength;

public:
    Connection(string address, int port, int bufferSize);
    ~Connection();
    int reciveData();
};

Connection::Connection(string address, int port, int bufferSize)
{
    this->addressLength = sizeof(this->server);

    this->sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);

    if(this->sock == -1)
    {
        cout << "Socket error!" << endl;
        exit(1);
    }

    memset(&(this->server), 0, sizeof(this->server));
    this->server.sin_family = AF_INET;
    this->server.sin_port = htons(port);
    this->server.sin_addr.s_addr = htonl(INADDR_ANY);

    if( bind(this->sock, (sockaddr *) &(this->server), this->addressLength) == -1 )
    {
        cout << "Bind socket error!" << endl;
        exit(1);
    }

    this->bufferSize = bufferSize;
    this->buffer = new char[bufferSize];

    cout << "Socket created!" << endl;
}

int Connection::receiveData()
{
    int returned;
    fflush(stdout);

    if( (returned =recvfrom(this->sock, this->buffer, this->bufferSize, 0, (sockaddr *) &(this->other), &this->addressLength)) == -1)
    {
        cout << "Receiving error!" << endl;
        exit(1);
    }

    return returned;
}

当我调用receiveData()时什么都没有发生-我想程序会等待一些udp包（我不知道他为什么没有收到它）。
有人能解释一下udp服务器和客户端程序的区别吗？
谢谢。

最佳答案

调用recvfrom()时，您将向它传递一个指向this->addressLength的指针。输入时，长度必须是地址缓冲区的完整大小。输出时，返回实际地址长度。因此recvfrom()可能会改变您的addressLength成员，影响后续代码。请改用局部变量：

int Connection::receiveData()
{
    int returned;
    int addrlen = sizeof(this->other);

    fflush(stdout);

    returned = recvfrom(this->sock, this->buffer, this->bufferSize, 0, (sockaddr *) &(this->other), &addrLen);
    if( returned == -1 )
    {
        cout << "Receiving error!" << endl;
        exit(1);
    }

    return returned;
}

或者，改用单独的成员变量：

class Connection
{
private:
    char * buffer;
    int bufferSize;
    int sock;
    struct sockaddr_in server;
    struct sockaddr_in other;
    socklen_t serverAddressLength;
    socklen_t otherAddressLength;

public:
    Connection(string address, int port, int bufferSize);
    ~Connection();
    int reciveData();
};

Connection::Connection(string address, int port, int bufferSize)
{
    this->serverAddressLength = sizeof(this->server);

    this->sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);

    if(this->sock == -1)
    {
        cout << "Socket error!" << endl;
        exit(1);
    }

    if(this->sock == -1)
    {
        cout << "Socket error!" << endl;
        exit(1);
    }

    memset(&(this->server), 0, sizeof(this->server));
    this->server.sin_family = AF_INET;
    this->server.sin_port = htons(port);
    this->server.sin_addr.s_addr = htonl(INADDR_ANY);

    if( bind(this->sock, (sockaddr *) &(this->server), this->serverAddressLength) == -1 )
    {
        cout << "Bind socket error!" << endl;
        exit(1);
    }

    this->bufferSize = bufferSize;
    this->buffer = new char[bufferSize];

    cout << "Socket created!" << endl;
}

int Connection::receiveData()
{
    int returned;
    fflush(stdout);

    this->otherAddressLength = sizeof(this->other);
    if( (returned =recvfrom(this->sock, this->buffer, this->bufferSize, 0, (sockaddr *) &(this->other), &this->otherAddressLength)) == -1)
    {
        cout << "Receiving error!" << endl;
        exit(1);
    }

    return returned;
}

关于c++ - 无法使用udp协议(protocol)从网络接收数据，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/17733794/