[asio-users] Boost asio - udp server

[Gheorghe Marinca]

I saw the official async udp server example from boost doc. There you
create a single udp socket, bind it to a local port and do something like
this:

socket(ioService,
boost::asio::ip::udp::endpoint(boost::asio::ip::udp::v4(), port))

socket.async_receive_from(buffer(data, max_length), senderEndpoint,
boost::bind(&Request::HandleReceiveFrom, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));

How can I handle multiple concurrent udp connections from clients, because
if I try to create another socket using

socket(ioService,
boost::asio::ip::udp::endpoint(boost::asio::ip::udp::v4(), port))

i get bind errors because I already have a socket bound to the same port

Some more about the udp server I want to implement. I use my server as a
dns proxy. I want to handle multiple clients, proxy their requests, and
give answers back.
If I could use something like tcp acceptor, but for udp that would simplify
things as I see them now.

Best regards,
-Ghita

[svante karlsson]

UDP is connectionless
You will receive all data sent from all your clients on the same server port.

/svante

I saw the official async udp server example from boost doc. There you create
socket(ioService, boost::asio::ip::udp::endpoint(boost::asio::ip::udp::v4(),
port))
socket.async_receive_from(buffer(data, max_length), senderEndpoint,
boost::bind(&Request::HandleReceiveFrom, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
How can I handle multiple concurrent udp connections from clients, because
if I try to create another socket using
socket(ioService, boost::asio::ip::udp::endpoint(boost::asio::ip::udp::v4(),
port))
i get bind errors because I already have a socket bound to the same port
Some more about the udp server I want to implement. I use my server as a dns
proxy. I want to handle multiple clients, proxy their requests, and give
answers back.
If I could use something like tcp acceptor, but for udp that would simplify
things as I see them now.
Best regards,
-Ghita
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[Gheorghe Marinca]

So the way to go in this case is the remeber the sender endpoint
ip::udp::endpoint and when I want to replay to a particular client just
create a new udp socked constructed with sender endpoint ?
I guess I should not have issues with address reuse because the remote
endpoint / server ip/port pair is unique then.

Post by svante karlsson
UDP is connectionless
You will receive all data sent from all your clients on the same server port.
/svante

Post by Gheorghe Marinca
I saw the official async udp server example from boost doc. There you

create

Post by Gheorghe Marinca
socket(ioService,

boost::asio::ip::udp::endpoint(boost::asio::ip::udp::v4(),

Post by Gheorghe Marinca
port))
socket.async_receive_from(buffer(data, max_length), senderEndpoint,
boost::bind(&Request::HandleReceiveFrom, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
How can I handle multiple concurrent udp connections from clients,

because

Post by Gheorghe Marinca
if I try to create another socket using
socket(ioService,

boost::asio::ip::udp::endpoint(boost::asio::ip::udp::v4(),

Post by Gheorghe Marinca
port))
i get bind errors because I already have a socket bound to the same port
Some more about the udp server I want to implement. I use my server as a

dns

Post by Gheorghe Marinca
proxy. I want to handle multiple clients, proxy their requests, and give
answers back.
If I could use something like tcp acceptor, but for udp that would

simplify

Post by Gheorghe Marinca
things as I see them now.
Best regards,
-Ghita

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Post by Gheorghe Marinca
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[Green, Cliff]

You do not need to create a socket for the reply - just send a datagram back to the source ("sent from") address. This is a pretty common use case.

Cliff

From: Gheorghe Marinca [mailto:***@gmail.com]
Sent: Tuesday, August 28, 2012 3:01 AM
To: asio-***@lists.sourceforge.net
Subject: Re: [asio-users] Boost asio - udp server

So the way to go in this case is the remeber the sender endpoint ip::udp::endpoint and when I want to replay to a particular client just create a new udp socked constructed with sender endpoint ?

[Gheorghe Marinca]

How to I send a datagram back without constructing a socket? What API to
use?

You do not need to create a socket for the reply – just send a datagram
back to the source (“sent from”) address. This is a pretty common use case.
****
** **
Cliff****
** **
*Sent:* Tuesday, August 28, 2012 3:01 AM
*Subject:* Re: [asio-users] Boost asio - udp server****
** **
So the way to go in this case is the remeber the sender endpoint
ip::udp::endpoint and when I want to replay to a particular client just
create a new udp socked constructed with sender endpoint ?
****
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[Cliff Green]

Use the UDP receive_from and send_to methods (the async versions have “async” in the method name).

Cliff


From: Gheorghe Marinca
Sent: Tuesday, August 28, 2012 10:43 AM
To: asio-***@lists.sourceforge.net
Subject: Re: [asio-users] Boost asio - udp server

How to I send a datagram back without constructing a socket? What API to use?

On Aug 28, 2012 7:07 PM, "Green, Cliff" <***@boeing.com> wrote:

You do not need to create a socket for the reply – just send a datagram back to the source (“sent from”) address. This is a pretty common use case.



Cliff



From: Gheorghe Marinca [mailto:***@gmail.com]
Sent: Tuesday, August 28, 2012 3:01 AM
To: asio-***@lists.sourceforge.net
Subject: Re: [asio-users] Boost asio - udp server



So the way to go in this case is the remeber the sender endpoint ip::udp::endpoint and when I want to replay to a particular client just create a new udp socked constructed with sender endpoint ?




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[Gheorghe Marinca]

I do not find for some reason these non member functions in online
documentation.. That is without creating a udp socket.

Post by Cliff Green
Use the UDP receive_from and send_to methods (the async versions have
“async” in the method name).
Cliff
*Sent:* Tuesday, August 28, 2012 10:43 AM
*Subject:* Re: [asio-users] Boost asio - udp server
How to I send a datagram back without constructing a socket? What API to use?

You do not need to create a socket for the reply – just send a datagram
back to the source (“sent from”) address. This is a pretty common use case.
****
****
Cliff****
****
*Sent:* Tuesday, August 28, 2012 3:01 AM
*Subject:* Re: [asio-users] Boost asio - udp server****
****
So the way to go in this case is the remeber the sender endpoint
ip::udp::endpoint and when I want to replay to a particular client just
create a new udp socked constructed with sender endpoint ?
****
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[Cliff Green]

Method == member function (typical terminology). Here’s the web page:

http://www.boost.org/doc/libs/1_51_0/doc/html/boost_asio/reference/ip__udp/socket.html

Cliff

From: Gheorghe Marinca
Sent: Tuesday, August 28, 2012 11:56 AM
To: asio-***@lists.sourceforge.net
Subject: Re: [asio-users] Boost asio - udp server

I do not find for some reason these non member functions in online documentation.. That is without creating a udp socket.

On Aug 28, 2012 9:12 PM, "Cliff Green" <***@codewrangler.net> wrote:

Use the UDP receive_from and send_to methods (the async versions have “async” in the method name).

Cliff


From: Gheorghe Marinca
Sent: Tuesday, August 28, 2012 10:43 AM
To: asio-***@lists.sourceforge.net
Subject: Re: [asio-users] Boost asio - udp server

How to I send a datagram back without constructing a socket? What API to use?

On Aug 28, 2012 7:07 PM, "Green, Cliff" <***@boeing.com> wrote:

You do not need to create a socket for the reply – just send a datagram back to the source (“sent from”) address. This is a pretty common use case.



Cliff



From: Gheorghe Marinca [mailto:***@gmail.com]
Sent: Tuesday, August 28, 2012 3:01 AM
To: asio-***@lists.sourceforge.net
Subject: Re: [asio-users] Boost asio - udp server



So the way to go in this case is the remeber the sender endpoint ip::udp::endpoint and when I want to replay to a particular client just create a new udp socked constructed with sender endpoint ?




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[Jeff Koftinoff]

You already have a UDP socket; the one the request was received from.

Jeff

Post by Cliff Green
I do not find for some reason these non member functions in online documentation.. That is without creating a udp socket.
Use the UDP receive_from and send_to methods (the async versions have “async” in the method name).
Cliff
From: Gheorghe Marinca
Sent: Tuesday, August 28, 2012 10:43 AM
Subject: Re: [asio-users] Boost asio - udp server
How to I send a datagram back without constructing a socket? What API to use?
You do not need to create a socket for the reply – just send a datagram back to the source (“sent from”) address. This is a pretty common use case.
Cliff
Sent: Tuesday, August 28, 2012 3:01 AM
Subject: Re: [asio-users] Boost asio - udp server
So the way to go in this case is the remeber the sender endpoint ip::udp::endpoint and when I want to replay to a particular client just create a new udp socked constructed with sender endpoint ?
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[Gheorghe Marinca]

Coming back to my udp server implementation. I read client requests on port
53 (DNS proxy), forward them to a name server and when that replay comes
back I want to replay to my clients using the same source port (53)
What I have been doing until now was to use only a socket on server (bound
to port 53) and receive all requests on that socket, but replayed to
clients using udp::socket::sent_to(clientEndpoint)

What happens is that clients outside of local machine (only) would not
recognize datagrams sent from my server to them because when I replay I use
a different source port than port 53 where they sent requests to.
It's something like that

D1(Source 192.168.1.1: port 1234, Destination server : port 53)
D2(Source server:* port 2331*, Destination 192.168.1.1: port 1234)

Is there a way to send clients response back without using the socket that
I originally received requests to ?

You do not need to create a socket for the reply – just send a datagram
back to the source (“sent from”) address. This is a pretty common use case.
****
** **
Cliff****
** **
*Sent:* Tuesday, August 28, 2012 3:01 AM
*Subject:* Re: [asio-users] Boost asio - udp server****
** **
So the way to go in this case is the remeber the sender endpoint
ip::udp::endpoint and when I want to replay to a particular client just
create a new udp socked constructed with sender endpoint ?
****
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