java DatagramSocket 接收数据 Multicast Socket 发送数据
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java DatagramSocket receive data Multicast Socket send data
提问by evan
can anyone show me an example in java to receive data from DatagramSocket and sending same data through Multicast Socket
任何人都可以在java中向我展示一个示例来从DatagramSocket接收数据并通过多播套接字发送相同的数据
采纳答案by Mohamed Saligh
Sending multicast datagrams
发送组播数据报
In order to send any kind of datagram in Java, be it unicast, broadcast or multicast, one needs a java.net.DatagramSocket:
为了在 Java 中发送任何类型的数据报，无论是单播、广播还是多播，都需要一个java.net.DatagramSocket：
DatagramSocket socket = new DatagramSocket();
One can optionally supply a local port to the DatagramSocket constructor to which the socket must bind. This is only necessary if one needs other parties to be able to reach us at a specific port. A third constructor takes the local port AND the local IP address to which to bind. This is used (rarely) with multi-homed hosts where it is important on which network adapter the traffic is received.
可以选择为套接字必须绑定到的 DatagramSocket 构造函数提供本地端口。仅当需要其他方能够在特定港口与我们联系时才需要这样做。第三个构造函数获取要绑定的本地端口和本地 IP 地址。这（很少）用于多宿主主机，其中接收流量的网络适配器很重要。
DatagramSocket socket = new DatagramSocket();
byte[] b = new byte[DGRAM_LENGTH];
DatagramPacket dgram;
dgram = new DatagramPacket(b, b.length,
InetAddress.getByName(MCAST_ADDR), DEST_PORT);
System.err.println("Sending " + b.length + " bytes to " +
dgram.getAddress() + ':' + dgram.getPort());
while(true) {
System.err.print(".");
socket.send(dgram);
Thread.sleep(1000);
}
Receiving multicast datagrams
接收组播数据报
One can use a normal DatagramSocket to send and receive unicast and broadcast datagrams and to send multicast datagrams. In order to receive multicast datagrams, however, one needs a MulticastSocket. The reason for this is simple, additional work needs to be done to control and receive multicast traffic by all the protocol layers below UDP.
可以使用普通的 DatagramSocket 来发送和接收单播和广播数据报以及发送多播数据报。然而，为了接收多播数据报，需要一个 MulticastSocket。原因很简单，需要做额外的工作来控制和接收 UDP 下所有协议层的多播流量。
byte[] b = new byte[BUFFER_LENGTH];
DatagramPacket dgram = new DatagramPacket(b, b.length);
MulticastSocket socket =
new MulticastSocket(DEST_PORT); // must bind receive side
socket.joinGroup(InetAddress.getByName(MCAST_ADDR));
while(true) {
socket.receive(dgram); // blocks until a datagram is received
System.err.println("Received " + dgram.getLength() +
" bytes from " + dgram.getAddress());
dgram.setLength(b.length); // must reset length field!
}
For more Information:
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回答by user207421
You've got that back to front. You receivemulticasts through a MulticastSocket, but you don't need to send them that way: you can send them via a DatagramSocket.
你已经回到了前面。您通过接收多播MulticastSocket，但您不需要以这种方式发送它们：您可以通过DatagramSocket.
See the Java Tutorial, Custom Networking trail.
请参阅Java 教程，自定义网络跟踪。
