客户端 接收端 ：

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using UnityEngine;
using UnityEngine.UI;

public class UDPServer : MonoBehaviour
{
    //以下默认都是私有的成员
    Socket socket;//目标socket
    EndPoint clientEnd;//客户端IP
    EndPoint ipEnd;//侦听端口
    public string recvStr; //接收的字符串
    string sendStr;//发送的字符串
    byte[] recvData = new byte[1024];//接收的数据，必须为字节
    byte[] sendData = new byte[1024];//发送的数据，必须为字节
    int recvLen;//接收的数据长度
    Thread connectThread;//连接线程

    // Start is called before the first frame update
    void Start()
    {
        InitSocket();
    }
    private void OnApplicationQuit()
    {
        SocketQuit();

    }
    // Update is called once per frame
    void Update()
    {
        //监听接受数据
        switch (recvStr)
        {
            //接收到的数据
            case "":
                //事件
                break;
               
		  }
    }
    void InitSocket()
    {
        // 定义侦听端口,侦听任何IP  自定义端口号和服务端保持一致
        ipEnd = new IPEndPoint(IPAddress.Any, 8883);//定义套接字类型,在主线程中定义
        socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);//服务端需要绑定ip
        socket.Bind(ipEnd);//定义客户端
        IPEndPoint sender = new IPEndPoint(IPAddress.Any, 8880);//自定义端口号 发送给别的某个电脑的 这台电脑的端口号
        clientEnd = (EndPoint)sender;
        //print("waiting for UDP dgram");
        //开启一个线程连接，必须的，否则主线程卡死
        connectThread = new Thread(new ThreadStart(SocketReceive));
        connectThread.Start();
    }

    public void SocketSend(string sendStr)
    {
        //清空发送缓存
        sendData = new byte[1024];//数据类型转换
        sendData = Encoding.UTF8.GetBytes(sendStr);//发送给指定客户端
        socket.SendTo(sendData, sendData.Length, SocketFlags.None, clientEnd);
    }

    void SocketReceive()
    {
        //进入接收循环
        while (true)
        {
            //对data清零
            recvData = new byte[1024];
            //获取客户端，获取客户端数据，用引用给客户端赋值
            recvLen = socket.ReceiveFrom(recvData, ref clientEnd);
            //print("message from:" + clientEnd.ToString());//打印客户端信息
            // 输出接收到的数据
            recvStr = Encoding.ASCII.GetString(recvData, 0, recvLen);

            print("我是服务器，接收到客户端的数据" + recvStr);
            //将接收到的数据经过处理再发送出去
            sendStr = "From Server333: " + recvStr;
            SocketSend(sendStr);

            //ProcessInformation(recvStr);
            // Debug.Log(sendStr);
        }

    }
    //连接关闭
    void SocketQuit()
    {
        //关闭线程
        if (connectThread != null)
        {
            connectThread.Interrupt();
            connectThread.Abort();
        }
        // 最后关闭socket
        if (socket != null)
            socket.Close();
        print("disconnect-1");
    }

}

服务器 发送端 ：

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
//服务器  发送端
public class UDPClient : MonoBehaviour
{
    public string recvStr;
    private string UDPClientIP;
    Socket socket;
    EndPoint serverEnd;
    IPEndPoint ipEnd;

    byte[] recvData = new byte[1024];
    byte[] sendData = new byte[1024];
    int recvLen = 0;
    Thread connectThread;


    private void Awake()
    {

    }
    void Start()
    {
        //IP地址
        UDPClientIP = "192.168.1.16";//自己电脑的ip地址
        UDPClientIP = UDPClientIP.Trim();
        InitSocket();
    }

    //ipEnd = new IPEndPoint(IP地址，端口号);
    //这里用json读取配置方便外部修改
    void InitSocket()
    {
        ipEnd = new IPEndPoint(IPAddress.Parse(UDPClientIP), 8880);// 后面的端口是接收端的端口号
        socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
        serverEnd = (EndPoint)sender;
        //开启一个线程连接
        connectThread = new Thread(new ThreadStart(SocketReceive));
        connectThread.Start();
    }

    //可以绑定Button发送string类型信息
    public void SocketSend(string sendStr)
    {
        //清空
        sendData = new byte[1024];
        //数据转换
        sendData = Encoding.UTF8.GetBytes(sendStr);
        //发送给指定服务端
        socket.SendTo(sendData, sendData.Length, SocketFlags.None, ipEnd);
    }

    //接收服务器信息
    void SocketReceive()
    {
        while (true)
        {

            recvData = new byte[1024];
            try
            {
                recvLen = socket.ReceiveFrom(recvData, ref serverEnd);
            }
            catch (Exception e)
            {
            }

            //print("信息来自: " + serverEnd.ToString());
            if (recvLen > 0)
            {
                recvStr = Encoding.UTF8.GetString(recvData, 0, recvLen);
                print(recvStr);
            }

            
        }
    }

    //连接关闭
    void SocketQuit()
    {
        //关闭线程
        if (connectThread != null)
        {
            connectThread.Interrupt();
            connectThread.Abort();
        }
        //最后关闭socket
        if (socket != null)
            socket.Close();
    }
    void OnApplicationQuit()
    {
        SocketQuit();
    }

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.K))
        {
            SocketSend("ddddd");
        }
    }

}