C#利用UdpClient發送廣播消息

首先寫個接受消息的客戶端。這裡偷了點懶，new UdpClient(11000)就是用Udp方式偵聽11000端口，偵聽任何發送到11000端口的消息都會接收到。

UdpClient udpClient = new UdpClient(11000); 
try 
{ 
    IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0); 
    Byte[] receiveBytes = udpClient.Receive(ref RemoteIpEndPoint); 
    string returnData = Encoding.ASCII.GetString(receiveBytes); 

    Console.WriteLine("This is the message you received " + 
                                 returnData.ToString()); 
    Console.WriteLine("This message was sent from " + 
                                RemoteIpEndPoint.Address.ToString() + 
                                " on their port number " + 
                                RemoteIpEndPoint.Port.ToString()); 

    udpClient.Close(); 
} 
catch (Exception e) 
{ 
    Console.WriteLine(e.ToString()); 
}

然後寫個發Udp的服務器

UdpClient udpClient = new UdpClient(11001); 
try 
{ 
    udpClient.Connect(IPAddress.Parse("192.168.0.255"), 11000);  
    Byte[] sendBytes = Encoding.ASCII.GetBytes("Is anybody thereA?"); 

    udpClient.Send(sendBytes, sendBytes.Length); 

    udpClient.Close();

} 
catch (Exception e) 
{ 
    Console.WriteLine(e.ToString()); 
}

其中192.168.0.255是你的內網廣播地址，11000是客戶端的端口。

廣播地址是通過你的子網掩碼獲得的例如你的網關是192.168.0.1，掩碼是255.255.255.0，那麼你的廣播地址就是192.168.0.255.