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Smartlink with two Flex Radios

Brent Parker
Brent Parker Member ✭✭
edited June 2020 in SmartSDR for Windows

Friday afternoon, I went thru the upgrade to V 2.0 with Smartlink. It went very smooth. Installed the ver 2 on my computer. Connected to the radio (6500), and of course it wanted to upgrade the radio. Pretty soon the purchase button showed up and I did that with a credit card. With the refresh, it was ready very quickly. Finally once connected with the new version, I setup the Smartlink stuff. I created a user, and configured the radio. When I tested the network, as I expected the port forwarding failed. I run a commercial type router and I expected I'd need to manually set the two ports.

I open up the router interface and forwarded port 4994 of tcp type to the radio and then 4993 of udp type to the radio. With that, the network passed. I tested it by running remote via vpn from my office and ran smartsdr from there, and it connected right up to Smartlink.

So far so good.

Then I upgraded the second radio. Same procedure and same flawless install.

The small hiccup was the port forwarding. I knew I needed to use different ports, because if I used the same ones, it would be going to the first radio.

So, I used port 4992 and 4991. But, and here is the biggie. While the traffic comes into my internet on one address, and it comes in on those second ports, and then gets forwarded to the internal ip address of the second radio, you still need to send it to the radio on port 4994 and 4993.

So on radio two, ip traffic comes in on the single Wan address for radio two, on 4992/4991, but then as it passes thru the router it gets directed to the second ip address of the radio, but it goes back to port 4994/4993. The radio only know about the two ports

Typically when you are passing port forwarding thru a router, you come in and pass thru on the same port number. In this case you don't, and need to translate back up!

Hope this may help someone else.


  • Jim Gilliam
    Jim Gilliam Member ✭✭
    edited December 2019

    I find your explanation about as clear as mud.

    Jim, K6QE

  • NX6D Dave
    NX6D Dave Member ✭✭
    edited December 2019
    Exactly correct.  Ports are objects on hosts and hosts are enumerated by the IP addresses assigned to their network interfaces.  The radio has one network interface (that I know of) and one set of ports.  To send a message to any device, you must send to an IP address Port pair.

    If you have more than one radio in your net, each one will have its own IP address and its own pair of ports.  Externally, the router makes the two radios and any other computers in the LAN look like they are a single computer using a single network interface with a single IP address bound to it.  This is the point of Network Address Translation, NAT.

    If you have two radios in the LAN, each will have a unique local network IP address and each will listen on the same fixed ports.  When their traffic flows through the router, in either direction, the IP addresses and the port number get mapped to new values.
  • Ted  VE3TRQ
    Ted VE3TRQ Member ✭✭✭
    edited August 2017
    Brent Parker's post is direct, to the point and accurate. Any one with passing familiarity with NAT would recognize this. NAT allows multiple (usually local or private) IP addresses behind a router to appear with a single (usually public) IP address to the outside world. The correct address behind the router is reached using port mapping - an outside port is mapped to a (potentially) different inside port and its associated IP address. That's what Brent is talking about. The outside traffic needs to get to an inside IP/port pair (referred to internally as a socket). NAT looks after the redirecting. In Brent's case, he is using port forwarding to control the process instead of allowing it to be automatic (which won't work in the case of multiple Flex radio servers on the private network). I hope that doesn't sound just as obtuse. If so, maybe reading up on networking is advisable. Ted VE3TRQ
  • Brent Parker
    Brent Parker Member ✭✭
    edited August 2017
    Most owners have one flex radio and a router that responds to automatic UPnP setup and can ignore this topic.However if you need to do a manual setup or have two radios, then you have to "dig under the hood" some, which this describes. Thank you to VE3TRQ and NX6D for confirming this approach. It took me a few minutes when setting this up to realize the second radio still want's it's ports coming in the default (4994/4993) even though it's not coming over the internet that way.
  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited June 2020
    I would suggest forwarding external port 21000 and 22000 to the ipaddress and local ports asked from the first rig. Then forward external ports 21010 and 22010 to the ipaddress and the local ports asked from the second rig. For example.....for the first rig.(assuming a reserved ip of Forward external port 21000 to ip port 4994 TCP Forward external port 22000 to ip port 4993 UDP Enter the external port numbers in the setup of SmartLink .for the first rig. Then for the second rig (assuming a reserved ip of Forward external port 21010 to ip port 4994 TCP Forward external port 22010 to ip port 4993 UDP See if that works. The external port is the port number used by the outside client, but once in your LAN, the info is forwarded to the rig defined by the forwarding rules... If this is not the proper way, I am sure one of the other experts will educate me.....

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