Can UDP socket support multicast using AT commands?

[ftdiyun]

Thanks

[pratik]

Yes, it does.
If you have many devices listening to the same post, you can send a packet to the UDP broadcast address (instead of a particular device), which will be broadcast to all the other devices that are listening.
The broadcast address is the last host address within the range defined by the subnet mask.

[ftdiyun]

Hi Pratik,
Thanks for your reply. Can you share an example using the AT commands for UDP multicast? Thanks.

[akouz]

• AT+CIPSTART=4,"UDP","192.168.1.255",1300,1300,2 - command to module: open connection 4, UDP, broadcast address, port 1300, time-out 2 sec
• 4,CONNECT
  OK - module replies
• AT+CIPSEND=4,16 - command to module: connection 4, 16 bytes to send
• OK
  > - module is ready to read data
• send 16 bytes of data
• Recv 16 bytes
  SEND OK - module replies
• AT+CIPCLOSE=4 - command to module: close connection 4
• 4,CLOSED
  OK - module replies

[ftdiyun]

Hi akouz,

Thanks for your information. It basically works.
A minor feedback of this "AT+CIPSTART=4,"UDP","192.168.1.255",1300,1300,2 - command to module: open connection 4, UDP, broadcast address, port 1300, time-out 2 sec", 2 is not time-out for UDP, but it is for TCP. For UPD transmission, it is UDP mode.

One more question, for UDP broadcasting, how should we know where is the message received from? To implement recvfrom function, we need to know the client's IP address and port number. Can you suggest which API in the SDK can be used? Thanks.

[lucio.macellari.mac]

Hi,

I need to receive broadcast UDP datagrams with AT commands but it does not work.
Using the following command

AT+CIPSTART=4,"UDP","0",0,1300,2

the 8266 only receive datagrams directed to its own IP and does not receive broadcasts.

Someone can help?

[RogerFL]

The problem I see is that if you do not know the netmask then you cannot know the broadcast address.
(The examples above only work when the netask is 0xFFFFFF00.)
I do not see any way to get the netmask with the AT commands. Is there a way?