Socket programming with UDP

1. UDP: no “connection” between client & server sender explicitly attaches IP destination address and port # to each packet receiver extracts sender IP address and port# from received packet UDP: transmitted data may be lost or received out-of-order Socket programming with UDP

2. Why UDP? • When receiving a msg, all the data can be extracted directly. • Can extract sender’s IP and Port#. • UDP provides unreliable transfer of groups of bytes (“datagrams”) between client and server • loss, out of order • Applications (tolerant loss and mis-order )? • Games? Audio/Video? • Additional code maybe needed.

3. UDP Socket Communications Server Client Recv Send Server Socket Client Socket Send Recv Client Socket Client Socket

4. create socket: Create datagram with serverIP and port=x; send datagram viaclient->Send( data, data->Length, L“serverIP", 12345 ); UdpClient ^ client = gcnew UdpClient( 0 ) ; read datagram from IPEndPoint ^receivePoint = gcnew IPEndPoint( IPAddress::Any, 0 ); array<Byte>^ data = client->Receive( receivePoint ); Close client Client/server socket interaction: UDP server (running on serverIP) client create socket, port= x: UdpClient ^ client = gcnew UdpClient( 12345 ); IPEndPoint ^receivePoint = gcnew IPEndPoint( IPAddress::Any, 0 ); read datagram from array<Byte>^ data = client->Receive( receivePoint ); write reply to client->Send( data, data->Length, receivePoint ); specifying client address, port number

5. UDP Sockets in C++/CLI Server Client • UdpClient ^ client = gcnew UdpClient( 12345 ) • IPEndPoint ^receivePoint = gcnew IPEndPoint( IPAddress::Any, 0 ); • array<Byte>^ data = client->Receive( receivePoint ); • client->Send( data, data->Length, receivePoint ); • UdpClient ^ client = gcnew UdpClient( 0 ) ; • client->Send( data, data->Length, L“127.0.0.1", 12345 ); • IPEndPoint ^receivePoint = gcnew IPEndPoint( IPAddress::Any, 0 ); • array<Byte>^ data = client->Receive( receivePoint );

6. An Example