[Gambas-user] UDP hole punching

[John Dovey]

What I do know, that this was a truly educational post. Never heard it
explained better. I’ve always just sent out a UDP packet with the same
hopeful faith that people put messages in a bottle, with next to no
expectation that it will ever be delivered … ;-)

John


On Tue, Jun 1, 2021 at 7:32 PM Dimitris Anogiatis <dosida at gmail.com> wrote:

> Brian G,
>
> A silly question. So in essence is hole punching just basically using an
> external server S to connect two clients A and B without doing port
> forwarding on each other's router?
>
> On Tue, Jun 1, 2021 at 5:28 PM Brian G <brian at westwoodsvcs.com> wrote:
>
>> I thought the nat took care of that..
>>
>> Flow:
>>
>> A and B each begin a UDP conversation with S; the NAT devices NA and NB
>> create UDP translation states and assign temporary external port numbers
>> EPA and EPB.
>>
>> S examines the UDP packets to get the source port used by NA and NB (the
>> external NAT ports EPA and EPB).
>>
>> S passes EIPA:EPA to B and EIPB:EPB to A.
>>
>> A sends a packet to EIPB:EPB.
>>
>> NA examines A's packet and creates the following tuple in its translation
>> table: (Source-IP-A, EPA, EIPB, EPB).
>>
>> B sends a packet to EIPA:EPA.
>>
>> NB examines B's packet and creates the following tuple in its translation
>> table: (Source-IP-B, EPB, EIPA, EPA).
>>
>> Depending on the state of NA's translation table when B's first packet
>> arrives
>>    (i.e. whether the tuple (Source-IP-A, EPA, EIPB, EPB) has been created
>> by the time of arrival of B's first packet),
>>    B's first packet is dropped (no entry in translation table) or passed
>> (entry in translation table has been made).
>>
>> Depending on the state of NB's translation table when A's first packet
>> arrives
>>    (i.e. whether the tuple (Source-IP-B, EPB, EIPA, EPA) has been created
>> by the time of arrival of A's first packet),
>>    A's first packet is dropped (no entry in translation table) or passed
>> (entry in translation table has been made).
>>
>> At worst, the second packet from A reaches B; at worst the second packet
>> from B reaches A.
>>    Holes have been "punched" in the NAT and both hosts can directly
>> communicate.
>>
>>
>> From this it looks like your app get a message from S the go between
>> containing the ip and port and then creates an outbound connection to the
>> other host
>> looks like you just need to read s's message and create a new udp
>> connection to B.
>>
>> Maybe I am just miss reading or don't get what you are doing.
>>
>> Do you have a sample program?
>>
>> "Failure is the key to success;
>>  each mistake teaches us something"  .. Morihei Ueshiba
>> Brian G
>>
>> ----- On Jun 1, 2021, at 10:43 AM, Mayost Sharon sharon at 455.co.il wrote:
>>
>> > Hello to you
>> >
>> > Can it be done:
>> > UDP hole punching
>> > Through:
>> > gb.net
>> >
>> > I understand that I need to change:
>> > UdpSocket.SourceHost and UdpSocket.SourcePort
>> > And they are for reading only
>> > They cannot be changed
>> >
>> > Is there another way to perform: UDP hole punching
>> >
>> > Thank you
>> >
>> > ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
>>
>> ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
>>
>
> ----[ http://gambaswiki.org/wiki/doc/netiquette ]----
>
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