class EE::Network::UdpSocket

Overview

Specialized socket using the UDP protocol. More…

#include <udpsocket.hpp>

class UdpSocket: public EE::Network::Socket {
public:
    // enums

    enum {
        MaxDatagramSize =            65507,
    };

    // methods

    static UdpSocket* New();
    unsigned short getLocalPort() const;
    Status bind(unsigned short port, const IpAddress& address = IpAddress::Any);
    void unbind();
    Status send(const void* data, std::size_t size, const IpAddress& remoteAddress, unsigned short remotePort);
    Status receive(void* data, std::size_t size, std::size_t& received, IpAddress& remoteAddress, unsigned short& remotePort);
    Status send(Packet& packet, const IpAddress& remoteAddress, unsigned short remotePort);
    Status receive(Packet& packet, IpAddress& remoteAddress, unsigned short& remotePort);
    void setSendTimeout(SocketHandle sock, const Time& timeout);
    void setReceiveTimeout(SocketHandle sock, const Time& timeout);
};

Inherited Members

public:
    // enums

    enum {
        AnyPort = 0,
    };

    enum Status;

    // methods

    void setBlocking(bool blocking);
    bool isBlocking() const;

Detailed Documentation

Specialized socket using the UDP protocol.

A UDP socket is a connectionless socket. Instead of connecting once to a remote host, like TCP sockets, it can send to and receive from any host at any time.

It is a datagram protocol: bounded blocks of data (datagrams) are transfered over the network rather than a continuous stream of data (TCP). Therefore, one call to send will always match one call to receive (if the datagram is not lost), with the same data that was sent.

The UDP protocol is lightweight but unreliable. Unreliable means that datagrams may be duplicated, be lost or arrive reordered. However, if a datagram arrives, its data is guaranteed to be valid.

UDP is generally used for real-time communication (audio or video streaming, real-time games, etc.) where speed is crucial and lost data doesn’t matter much.

Sending and receiving data can use either the low-level or the high-level functions. The low-level functions process a raw sequence of bytes, whereas the high-level interface uses packets (see Packet), which are easier to use and provide more safety regarding the data that is exchanged. You can look at the Packet class to get more details about how they work.

It is important to note that UdpSocket is unable to send datagrams bigger than MaxDatagramSize. In this case, it returns an error and doesn’t send anything. This applies to both raw data and packets. Indeed, even packets are unable to split and recompose data, due to the unreliability of the protocol (dropped, mixed or duplicated datagrams may lead to a big mess when trying to recompose a packet).

If the socket is bound to a port, it is automatically unbound from it when the socket is destroyed. However, you can unbind the socket explicitely with the Unbind function if necessary, to stop receiving messages or make the port available for other sockets.

Usage example:

// ----- The client -----

// Create a socket and bind it to the port 55001
UdpSocket socket;
socket.bind(55001);

// Send a message to 192.168.1.50 on port 55002
std::string message = "Hi, I am " + IpAddress::getLocalAddress().toString();
socket.Send(message.c_str(), message.size() + 1, "192.168.1.50", 55002);

// Receive an answer (most likely from 192.168.1.50, but could be anyone else)
char buffer[1024];
std::size_t received = 0;
IpAddress sender;
unsigned short port;
socket.receive(buffer, sizeof(buffer), received, sender, port);
std::cout << sender.toString() << " said: " << buffer << std::endl;

// ----- The server -----

// Create a socket and bind it to the port 55002
UdpSocket socket;
socket.bind(55002);

// Receive a message from anyone
char buffer[1024];
std::size_t received = 0;
IpAddress sender;
unsigned short port;
socket.receive(buffer, sizeof(buffer), received, sender, port);
std::cout << sender.toString() << " said: " << buffer << std::endl;

// Send an answer
std::string message = "Welcome " + sender.toString();
socket.send(message.c_str(), message.size() + 1, sender, port);

See also:

EE::Network::Socket, EE::Network::TcpSocket, EE::Network::Packet

Enum Values

MaxDatagramSize

The maximum number of bytes that can be sent in a single UDP datagram.

Methods

unsigned short getLocalPort() const

Get the port to which the socket is bound locally If the socket is not bound to a port, this function returns 0.

Returns:

Port to which the socket is bound

See also:

Bind

Status bind(unsigned short port, const IpAddress& address = IpAddress::Any)

Bind the socket to a specific port Binding the socket to a port is necessary for being able to receive data on that port. You can use the special value Socket::AnyPort to tell the system to automatically pick an available port, and then call GetLocalPort to retrieve the chosen port.

Parameters:

port	Port to Bind the socket to
address	Address of the interface to bind to

Returns:

Status code

See also:

Unbind, GetLocalPort

void unbind()

Unbind the socket from the local port to which it is bound The port that the socket was previously using is immediately available after this function is called. If the socket is not bound to a port, this function has no effect.

See also:

Bind

Status send(const void* data, std::size_t size, const IpAddress& remoteAddress, unsigned short remotePort)

Send raw data to a remote peer Make sure that size is not greater than UdpSocket::MaxDatagramSize, otherwise this function will fail and no data will be sent.

Parameters:

data	Pointer to the sequence of bytes to send
size	Number of bytes to send
remoteAddress	Address of the receiver
remotePort	Port of the receiver to send the data to

Returns:

Status code

See also:

Receive

Status receive(void* data, std::size_t size, std::size_t& received, IpAddress& remoteAddress, unsigned short& remotePort)

Receive raw data from a remote peer In blocking mode, this function will wait until some bytes are actually received. Be careful to use a buffer which is large enough for the data that you intend to receive, if it is too small then an error will be returned and all the data will be lost.

Parameters:

data	Pointer to the array to fill with the received bytes
size	Maximum number of bytes that can be received
received	This variable is filled with the actual number of bytes received
remoteAddress	Address of the peer that sent the data
remotePort	Port of the peer that sent the data

Returns:

Status code

See also:

Send

Status send(Packet& packet, const IpAddress& remoteAddress, unsigned short remotePort)

Send a formatted packet of data to a remote peer Make sure that the packet size is not greater than UdpSocket::MaxDatagramSize, otherwise this function will fail and no data will be sent.

Parameters:

packet	Packet to send
remoteAddress	Address of the receiver
remotePort	Port of the receiver to send the data to

Returns:

Status code

See also:

Receive

Status receive(Packet& packet, IpAddress& remoteAddress, unsigned short& remotePort)

Receive a formatted packet of data from a remote peer In blocking mode, this function will wait until the whole packet has been received.

Parameters:

packet	Packet to fill with the received data
remoteAddress	Address of the peer that sent the data
remotePort	Port of the peer that sent the data

Returns:

Status code

See also:

Send

void setSendTimeout(SocketHandle sock, const Time& timeout)

Set the send timeout. Only callable after bind ( after the socket has been initialized ).

void setReceiveTimeout(SocketHandle sock, const Time& timeout)

Set the receive timeout Only callable after bind ( after the socket has been initialized ).