UDP Sockets in C#

UDP provides an end-to-end service different from that of TCP.

In fact, UDP performs only two functions:

(1) it adds another layer of addressing (ports) to that of IP

(2) it detects data corruption that may occur in transit and discards any corrupted messages

Diffenence from TCP Sockets:

1. UDP sockets do not have to be connected before being used.

2. TCP is like telephone, and UDP is like email.

UDP Client

The typical UDP client goes through three steps:

1. Construct an instance of UdpClient, optionally specifying the local address and port.
2. Communicate by sending and receiving datagrams (byte arrays) using the Send() and
  Receive() methods of UdpClient.
3. When finished, deallocate the socket using the Close() method of UdpClient.

UdpEchoClient.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Zeus.Thunder.Core;
using System.Net; // For IPEndPoint
using System.Net.Sockets; // For UdpClient, SocketException

namespace SharpTrainer.NetWork
{
    class UdpEchoClient : ITestCase
    {
        public void Run()
        {
            Console.Write("Input Server IP: ");
            string server = Console.ReadLine();

            Console.Write("Input Server Port: ");
            int servPort = Int32.Parse(Console.ReadLine());

            Console.Write("Input Echo String: ");
            byte[] sendPacket = Encoding.ASCII.GetBytes(Console.ReadLine());

            // Create a UdpClient instance
            UdpClient client = new UdpClient();
            try 
            {
                // Send the echo string to the specified host and port
                client.Send(sendPacket, sendPacket.Length, server, servPort);
                Console.WriteLine("Sent {0} bytes to the server...", sendPacket.Length);

                // This IPEndPoint instance will be populated with the remote sender’s
                // endpoint information after the Receive() call
                IPEndPoint remoteIPEndPoint = new IPEndPoint(IPAddress.Any, 0);

                // Attempt echo reply receive
                byte[] rcvPacket = client.Receive(ref remoteIPEndPoint);

                Console.WriteLine("Received {0} bytes from {1}: {2}", rcvPacket.Length, remoteIPEndPoint,
                    Encoding.ASCII.GetString(rcvPacket, 0, rcvPacket.Length));
            } 
            catch (SocketException se) 
            {
                Console.WriteLine(se.ErrorCode + ": " + se.Message);
            }

            client.Close();
        }
    }
}

UdpEchoServer.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Zeus.Thunder.Core;
using System.Net; // For IPEndPoint
using System.Net.Sockets; // For UdpClient, SocketException

namespace SharpTrainer.NetWork
{
    class UdpEchoServer : ITestCase
    {
        public void Run()
        {
            Console.Write("Input Server Port: ");
            int servPort = Int32.Parse(Console.ReadLine());

            UdpClient client = null;
             try {
                // Create an instance of UdpClient on the port to listen on
                client = new UdpClient(servPort);
            } catch (SocketException se) {
                Console.WriteLine(se.ErrorCode + ": " + se.Message);
                Environment.Exit(se.ErrorCode);
            }

            // Create an IPEndPoint instance that will be passed as a reference
            // to the Receive() call and be populated with the remote client info
            IPEndPoint remoteIPEndPoint = new IPEndPoint(IPAddress.Any, 0);

            for (;;) 
            { 
                // Run forever, receiving and echoing datagrams
                try {
                    // Receive a byte array with echo datagram packet contents
                    byte[] byteBuffer = client.Receive(ref remoteIPEndPoint);
                    Console.Write("Handling client at " + remoteIPEndPoint + " - ");
                    // Send an echo packet back to the client
                    client.Send(byteBuffer, byteBuffer.Length, remoteIPEndPoint);
                    Console.WriteLine("echoed {0} bytes.", byteBuffer.Length);
                } catch (SocketException se) {
                    Console.WriteLine(se.ErrorCode + ": " + se.Message);
                }
            }
        }
    }
}

运行结果:

Server端：

Handling client at 127.0.0.1:65005 - echoed 18 bytes.

Client端:

Input Server IP: 127.0.0.1
Input Server Port: 9999
Input Echo String: Hello Master HaKu!
Sent 18 bytes to the server...
Received 18 bytes from 127.0.0.1:9999: Hello Master HaKu!