Determine remote device endpoint UDP Clojure CLR

Trying to perform the equivalent c# code in Clojure CLR

using System.Net;
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
EndPoint remote = (EndPoint) sender;
recv = sock.ReceiveFrom(data, ref remote);

What I've tried in Clojure that does not work:

(let [
      sender (IPEndPoint. (IPAddress/Any) 0)
      ^EndPoint remote ^EndPoint sender
      recv (.ReceiveFrom sock data (by-ref remote))
      ]
      (println (.ToString remote))
      ;; Do something with data...
 )

It just shows 0.0.0.0:0 I'm thinking the ref is not working but also not sure of the hint / cast syntax.

I've looked at here for info on ref https://github.com/richhickey/clojure-clr/wiki/CLR-Interop And here about specifying types: https://github.com/clojure/clojure-clr/wiki/Specifying-types

Solution

I translated the MSDN article cited in the comments on the question.

(ns test.me
    (:import [System.Net IPHostEntry Dns IPEndPoint EndPoint IPAddress]
             [System.Net.Sockets Socket SocketType ProtocolType]))

(set! *warn-on-reflection* true)

(defn f []
   (let [hostEntry (Dns/GetHostEntry (Dns/GetHostName))
         endPoint (IPEndPoint. ^IPAddress (first (.AddressList hostEntry)) 11000)
         sender (IPEndPoint. (IPAddress/IPv6Any) 0)
         msg (byte-array 256)]       
     (with-open [s (Socket. (.AddressFamily (.Address endPoint))
                            SocketType/Dgram
                            ProtocolType/Udp)]
       (.Bind s endPoint)
       (.ReceiveFrom s  msg (by-ref sender))
       (println sender))))

Running it yields:

>Clojure.Main.exe
Clojure 1.7.0-master-SNAPSHOT
user=> (load "/test/me")
nil
user=> (in-ns 'test.me)
#object[Namespace 0xaca85c "test.me"]
test.me=> (f)
#object[IPEndPoint 0x2126697 [fefe::3030:cfdf:f7f7:ecec%11]:55056]
nil

(IP address edited)

You might need to adjust IPAddress/IPv6Any for your system.

The with-open form is used to automatically close the socket upon exit.

Note that very few type hints (one, actually) are needed. I have turned on reflection warnings -- that's the best way to determine if you need more hints. (In this case, without the ^IPAddress type hint, loading fails with an error because it cannot resolve the IPEndPoint constructor.)