0.1.0

src/natpmp.cr

@@ -70,8 +70,17 @@ module NatPMP
     def initialize(@gateway_ip : String, autoconnect : Bool = true)
       # The specification is IPV4 only!
       @socket = UDPSocket.new(Socket::Family::INET)
+      # A given host may have more than one independent
+      # NAT-PMP client running at the same time, and address announcements
+      # need to be available to all of them.  Clients should therefore set
+      # the SO_REUSEPORT option or equivalent in order to allow other
+      # processes to also listen on port 5350.
       @socket.reuse_port = true
       @socket.reuse_address = true
+      # Additionally, implementers
+      # have encountered issues when one or more processes on the same device
+      # listen to port 5350 on *all* addresses.  Clients should therefore
+      # bind specifically to 224.0.0.1:5350, not to 0.0.0.0:5350.
       @socket.bind 5350
       if autoconnect
         connect()
@@ -79,6 +88,7 @@ module NatPMP
     end
 
     def connect
+      # @socket.join_group(Socket::IPAddress.new("224.0.0.1", 5351))
       @socket.connect(@gateway_ip, 5351)
     end
 
@@ -99,6 +109,11 @@ module NatPMP
           @socket.receive(msg)
           break
         rescue IO::TimeoutError
+          # If no
+          # NAT-PMP response is received from the gateway after 250 ms, the
+          # client retransmits its request and waits 500 ms.  The client SHOULD
+          # repeat this process with the interval between attempts doubling each
+          # time.
           @socket.read_timeout = @socket.read_timeout.not_nil!*2
           next
         rescue
@@ -112,6 +127,9 @@ module NatPMP
       result_code = decode_msg(UInt16, msg[2..3])
       epoch = decode_msg(UInt32, msg[4..7])
 
+      # If the result code is non-zero, the value of the External
+      # IPv4 Address field is undefined (MUST be set to zero on transmission,
+      # and MUST be ignored on reception).
       if result_code != 0
         ip_address = nil
       else
@@ -120,7 +138,6 @@ module NatPMP
       return vers, op, result_code, epoch, ip_address
     end
 
-    # https://datatracker.ietf.org/doc/html/rfc6886#section-3.3
     def request_mapping(internal_port : UInt16, external_port : UInt16, operation : UInt8, lifetime : UInt32 = 7200)
       request = MappingPacket.new(internal_port, external_port, lifetime, operation).to_slice
       msg = Bytes.new(16)