Socket programming with UDP no connection between client

Socket programming with 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

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.

UDP Socket Communications Server Can receive from multiple clients, and send to them. Recv Create socket, Server Bind the socket to Socket an IPEnd. Point Send Client Send Recv Client Socket Create Client socket, Socket Bind the socket to an IPEnd. Point

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

UDP Sockets in C++/CLI Server • Udp. Client ^ client = gcnew Udp. Client( 12345 ) • IPEnd. Point ^receive. Point = gcnew IPEnd. Point( IPAddress: : Any, 0 ); • array<Byte>^ data = client>Receive( receive. Point ); • client->Send( data, data>Length, receive. Point ); Client • Udp. Client ^ client = gcnew Udp. Client( 0 ) ; • client->Send( data, data>Length, L“ 127. 0. 0. 1", 12345 ); • IPEnd. Point ^receive. Point = gcnew IPEnd. Point( IPAddress: : Any, 0 ); • array<Byte>^ data = client>Receive( receive. Point );

An Example