UDP receive datagram and answer it

Targets macOS
1

Hi, I"m using UDP for years now in several background apps for logging. Works perfect.

Question: Is it possible to send an answer directly to the client who was sending a datagram?

2

yes, you can just write a datagram:
to the IP Address of the sender and the port where the sender is listening on.

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3

Indeed! Within the socket directly a new datagram is working.

But, because UDP is connectionless, how long will routers keep this ‘route’ open?

4

There is no route to keep open. If the routers are configured correctly, the UDP broadcast should propagate.

If you want something more reliable, you could use a TCPSocket for the confirmation callback.

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5

Basicly as long as you have control (bound to) the port that receives you are ok.

Sending works like:
If you are not bound to a port for sending, set port to 0 and one will be used for outgoing packets.
As long as you send to an ip-address only that ip will receive it.
As long as you send to a broadcast address (ending at 255 mostly) all the upd listeners on the same port (you sent it to) will receive the package.

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