(急)udpClient.Receive(ref remotePoint)一直提示“在执行此操作前必须先调用 Bind 方法。”
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Text;
using System.Data;
using System.Windows.Forms;

namespace UDP
{
public class UDPClient
{
//设置一个timer，在发送或get数据的时候，判断5秒没有数据返回，则报连接不上
System.Timers.Timer timer = new System.Timers.Timer();

private IPEndPoint hostPoint;//服务器主机地址
private IPEndPoint remotePoint;//目标主机地址

private Thread listenThread;//监听线程
private UdpClient udpClient;

private bool bConnect = false;

public bool BConnect
{
get { return bConnect; }
set { bConnect = value; }
}

//类当前的状态
public UDPRETURNTYPE currenttype = UDPRETURNTYPE.NULL;

//singleton模式
private static UDPClient theclient;

//不可不带参数实例化
private UDPClient()
{

}

public static UDPClient instance(string ip)
{
theclient = new UDPClient(ip, "5006");
return theclient;
}
~UDPClient()
{
try
{
udpClient.Close();
listenThread.Abort();

}
catch
{ }
}

public void Close()
{
try
{
udpClient.Close();
listenThread.Abort();

}
catch
{ }
}

private UDPClient(string pserverIP, string pserverPort)
{
if (this.udpClient != null)
{
udpClient.Close();
udpClient = null;
}
//Console.WriteLine("我是客户端，我开始运行啦11！");
string serverIp = pserverIP;
int Port = int.Parse(pserverPort);
udpClient = new UdpClient();
remotePoint = new IPEndPoint(IPAddress.Any, 0);//提供任何端口和IP，这里不需要指定
hostPoint = new IPEndPoint(IPAddress.Parse(serverIp), Port);//实例化主机地址

//=========================一开始测试发送==========================
byte[] buffer;
buffer = System.Text.Encoding.UTF8.GetBytes(Convert.ToString((int)UDPTYPE.connect));

listenThread = new Thread(new ThreadStart(Run));
listenThread.Start();
this.timer.Interval = 500;
this.timer.Elapsed += new System.Timers.ElapsedEventHandler(timer_Elapsed);
}

int itime = 0;
void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{

if (itime >= 3000 && this.currenttype == UDPRETURNTYPE.NULL)
{
itime = 0;
timer.Stop();
MessageBox.Show(" 与上级计算机无法正常连接，请检查\r“数据传输地址”是否错误或联系管理员！");

}
else if (this.currenttype == UDPRETURNTYPE.SUCCESS)
{
itime = 0;

timer.Stop();
MessageBox.Show("与上级同步数据成功！");

}
else if (this.currenttype == UDPRETURNTYPE.FALSE)
{
itime = 0;

timer.Stop();
MessageBox.Show("与上级同步数据失败！");
}
itime += 500;

}

//=================== 外部调用的方法
public void GetMessage(string tbName, string sql)
{
string tempresult = "";
tempresult += Convert.ToString((int)UDPTYPE.get) + "###" + tbName + "###" + sql + "###";
try
{
byte[] buffer;
//发送数据buffer
buffer = System.Text.Encoding.UTF8.GetBytes(tempresult);
udpClient.Send(buffer, buffer.Length, hostPoint);
this.currenttype = UDPRETURNTYPE.NULL;
timer.Start();
//udpClient.Receive(ref hostPoint);
}
catch
{
//MessageBox.Show("信息获取失败，可能与上级连接计算机没连通，请检查IP或联系管理员！");
//Console.WriteLine("数据发送异常，可能是服务器接收软件没开");
}
}

public void ModifyMessage(DataTable dt, string dtname)
{
string tempresult = "";
//加上记录数
//tempresult += dt.Rows.Count.ToString() + "&&&";
//
tempresult += Convert.ToString((int)UDPTYPE.modify) + "###" + dtname + "###";
////////////type、dtname、cols以###分隔，rows以|rows|分隔,colname=colvalue|cols|colname===colvalue
//type####dtname####colname===colvalue|cols|colname1===colvalue1|rows|colname===colvalue|cols|colname1===colvalue1
tempresult += UDP.Base.DtToString(dt);
try
{
byte[] buffer;
//发送数据buffer
buffer = System.Text.Encoding.UTF8.GetBytes(tempresult);
udpClient.Send(buffer, buffer.Length, hostPoint);
this.currenttype = UDPRETURNTYPE.NULL;
timer.Start();
//udpClient.Receive(ref hostPoint);
}
catch
{
//MessageBox.Show("信息获取失败，可能与上级连接计算机没连通，请检查IP或联系管理员！");
//Console.WriteLine("数据发送异常，可能是服务器接收软件没开");
}
}

/**/
/// <summary>
/// 监听线程
/// </summary>
private void Run()
{
byte[] buffer;
while (true)
{
try
{
buffer = udpClient.Receive(ref remotePoint);//在这个地方提示在执行此操作前必须先调用 Bind 方法
bConnect = true;
if (buffer.Length > 0)
{
//Console.WriteLine(Encoding.UTF8.GetString(buffer, 0, buffer.Length));
string tempresult = Encoding.UTF8.GetString(buffer, 0, buffer.Length);
tempresult = UDP.Base.AnyData(tempresult, "client");
//currenttype =
switch (tempresult)
{
case "1":

currenttype = UDPRETURNTYPE.SUCCESS;
break;
case "2":
currenttype = UDPRETURNTYPE.FALSE;
break;
case "3":
currenttype = UDPRETURNTYPE.NULL;
break;
default:
currenttype = UDPRETURNTYPE.SUCCESS;
break;
}
//MessageBox.Show("数据更新，请刷新数据列表！");

}

}
catch (Exception ex)
{
string aa = ex.ToString();
bConnect = false;
}
Thread.Sleep(500);
}
}
}
}


[解决办法]
都告诉你了，你肯定没有连接上服务端，你家就Receive了，没看到你代码中有connect的方法
[解决办法]
If you intend to receive multicast datagrams, you must call the Bind method with a multicast port number.