GCDAsyncUdpSocket and multicast sending and receiving

Question

In first approach I create client-server app ,based on sampleProject , which send some data to server.

Legend:
sender
    address = reciver ip
    port = re         


        

Answer 1

1. Multicast addresses are special reserved addresses for multicasting purpose. When a host send a data to a multicast address (group), all hosts that have joined that group will receive the data.

2. Any host that wishes to receive data from a multicast group needs to join that group. The three steps for GCDAsyncUdpSocket are: (note that group address and group port combination must be unique for that selected multicast group)

   [_udpSocket bindToPort:_port error:&error];
   [_udpSocket joinMulticastGroup:_address error:&error];
   [_udpSocket beginReceiving:&error])
   

3. For a sender, you don't need these two lines as you have.

   [_udpSocket bindToPort:0 error:&error];  //bindToPort:0 is same as auto-select sender port by default.
   [_udpSocket beginReceiving:&error];   //if you don't want to received, no need for this.
   

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