Author Topic: Port Forwarding Entry 3389 Not Working on Thomson TG782T (BigPond) Router  (Read 623 times)

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Offline Greg67

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I have been using the Simple Port Forwarding (SPF) program to make my computer remotely accessible to computers using Microsoft's Remote Desktop program.  When I use the port testing function on SPF, I get the error message "3389_TCP_Port In Use_Failed".  I have some observations that might help you to diagnose the problem:

(1) The only firewall being used is Windows 10 (Pro) Defender.  The firewalls for the Thomson router and ESET Internet Security have been disabled.

(2) The IP adddress provided by is the same as that provided by the router.

(3) When I use the Resource Monitor Listening Ports function, I see four entries for port 3389 but they all have the same PID (1164) and same name "svchost.exe NetworkService".

(4) I have used Remote Desktop Assistant, Port Forwarding and Router Port Forwarding (RPF) programs previously on the same computer but all three apps have now been uninstalled.

(5) When I used RPF I was able to get remote access for my PC, but when I used it again a few days ago, the licence I bought was not recognised even though it was less than three months old and I
uninstalled it soon after.

Your consideration of this matter will be highly appreciated. :smiley:
Greg67 Forums

Offline trpted

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Let us do this step by step. Starting off with pre-checks.

********************** Pre-check item one  **********************

#1 Most ISP have a TOS ( Terms Of Service )

#2 You need to find that TOS for your ISP.

#3 If your ISP does not say anything that you can not to run any servers of any kind - green light.

#4 If your ISP does not allow you to run any servers of any kind - yellow light.

-> Be sure to know the risk of running any kind of server.

-> You have to decide is worth the risk or not, based upon...

a) easy you can get another ISP to serve you - for example.

b) much does it cost to upgrade the type of account that you have with your ISP. Example from regular consumer to gaming or business plan.

********************** Pre-check item two  **********************

#1 As how to check what the IP Address is/are, Subnet Mask is/are, Default Gateway is, MAC Address(es) is/are, DNS Server(s) are of your computer, it depends on the OS and Version.

#2 Note: This example assumes that you are on Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8 or Windows 10

a) Press the Windows Start key to open the Start screen.

b) Type cmd and press Enter to launch the command prompt.

Note: You do not need to click on anything on the Start screen—typing will automatically initiate a program search.

c) Type ipconfig /all at the command prompt to check the network card settings.

d) If not on Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8 or Windows 10 and you do not know how to check that network info - then post what is your OS and Version is.

#4 You need to make sure that the Default Gateway on your computer is the same LAN IP as your NAT router.

************* Pre-check item three  ***************

#1 Go to

#2 On that web page is the non bogan IPv4 (Public) Address that users from Internet use to connect to you.

#3 In your NAT router, somewhere in there you must have the same non bogan IP Address.

Example non bogan IP Address is 999.888.777.666, but in the NAT router the WAN IP is - this is not ok.

#4 Important note: This is not to say that the non bogan IP Address has to be Static.

Example yesterday's IP Address was 999.888.777.666 and today's IP Address is 999.888.777.555 - this is ok.

#5 If the WAN IP in the NAT router does not match the true WAN IP, well it matters what the WAN IP in the NAT router is.

a) If the WAN IP is from -, then CGNAT/NAT444/LSN is present.


If you want more details about CGNAT/NAT444/LSN, you can look at

The possible fixes to fix your issue if CGNAT/NAT444/LSN is present.

#1 Have them in their NAT router forward the ports to the WAN IP of your NAT router..

#2 Upgrading the type of plan that you are on with your ISP so that you get a non bogan WAN IP Address.

For example if you are a Residential Service Plan, consider going to a Business Service Plan.

#3 Consider switching to another ISP that can give you you a non bogan WAN IP Address.

#4 For the long term future, get IPv6 working.

b) If the WAN IP is one of the RFC 1918 IPs (Meaning to, from to OR from to and if your NAT router is a RJ-45 WAN port router:

Step 1: Physically find your NAT Router

Step 2: Find the WAN port of it.

Info: WAN port could be called Internet or To Modem or To ONT port.

Step 3: Report back what the brand and model of the device that is connected at the other end of the wire that is connected to the WAN port of the NAT router.

c) If the WAN IP is one of the RFC 1918 IPs and if your NAT router is NOT a RJ-45 WAN port router (or a gateway NAT router), then CGNAT/NAT444/LSN is present (See fix above if the case).

d) If the WAN IP is one of the RFC 1918 IPs  if your NAT router is a gateway NAT router, it matters how it is connected to the Internet (RJ-45 WAN port or acting a modem combo).

e) If the WAN IP is one of the RFC 1918 IPs and you do not know the type of NAT router yours is, it would help to know the brand and model it is - if you did not post already.

Since you posted the brand and model of your router, it (Thomson TG782T) is a modem combo.

f) If the WAN IP was not any of those, it would be a good idea to check to see how the non bogan IP Address is not the same (and not NAT). If you need help finding why that is, you are to asking for help doing so.

************* Pre-check item four  ***************

When forwarding manually remember to forward to your local IP Address, that is unless you are trying to forward some other computer (example to Xbox)

So if you get output...

IP Address
Subnet Mask
Default Gateway
At least one DNS

-> you would forward to

*** Rest of directions **

#1 if asked for a remote/source IP Address it goes like this.

a) Let us say that the fictional IP Address of 999.888.777.666 existed ( I can assure it does not as IPv4 is only to and IPv6 is all hex with colons between ), it was mine, I did not share my connection with others (parents/son/daughter), and you wanted to only allow me to connect through your NAT router to your computer - then it case you would type in 999.888.777.666

b) If you do not want to only allow only a certain IP Address (OR IP Address Range) to connect to you, it has to be either blank (not filled in) OR if you can not leave it blank then it has to be

#2 From DSLR ( -> Forums -> Broadband and Networking -> Networking -> How to know if ports are reaching my computer from outside the post by DSLR user mackey (user # 1479488) on 2015-Sep-24 at 8:05 pm - if you wanted to test port 5154, besides using an inbound client side port checker:

Run tcpdump (`tcpdump -p -n -i <interface> port 5154` would be a good command to start with). If you see incoming TCP SYN packets (not SYN/ACK), or incoming UDP packets from an IP which did not have an outgoing packet first, then the port is open.

b) For tcpdump on Windows I found this info

#3 For a TCP and a UDP port checker you can use

#4 Using a packet sniffer (like tcpdump = command line / like wireshark = GUI) you should see the traffic from an outside IP address reaching your computer, like I did (when you are forwarding the ports to your computer).

Code: [Select]
    user-name@pc-name:~$ tcpdump -p -n -i eth0 port 5154
    tcpdump: eth0: You don't have permission to capture on that device
    (socket: Operation not permitted)
    user-name@pc-name:~$ sudo tcpdump -p -n -i eth0 port 5154
    [sudo] password for user-name:
    tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
    listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
    08:40:24.169428 IP > UDP, length 6
    08:42:15.839461 IP > Flags [S], seq 1464127243, win 8192, options [mss 1460], length 0
    08:49:05.773987 IP > UDP, length 0
    08:49:06.938818 IP > UDP, length 0
    08:57:57.580814 IP > Flags [S], seq 3027635480, win 14600, options [mss 1460,sackOK,TS val 4240686068 ecr 0,nop,wscale 8], length 0
    08:57:57.712334 IP > Flags [S], seq 1267700791, win 14600, options [mss 1460,sackOK,TS val 4240686102 ecr 0,nop,wscale 8], length 0
    08:57:57.840328 IP > Flags [S], seq 1515263633, win 14600, options [mss 1460,sackOK,TS val 4240686134 ecr 0,nop,wscale 8], length 0
    7 packets captured
    7 packets received by filter
    0 packets dropped by kernel

#5 Some notes about my testing..

a) is from this same computer.

b) As noted at -> Services -> Shield's Up they own -thru-

c) I believe is from as it only checks TCP ports.

d) As you can see, I checked port 5154.

#6 The only UDP ports that checks, that I know of, are:

a) DNS (53) -> Freeware -> Utilities -> DNS Benchmark -> DNS Spoofability Test Introduction (or -> Services -> DNS Spoofability Test)

b) Universal Plug n'Play (UPnP) = 1900

From -> Services -> Shield's Up: Click on Proceed and then GRC's Instant UPnP Exposure Test.

#7 Here are some notes about listening:


a) If you are on Windows I point you to

b) If you are not on Windows (Mac, Unix/Linux), go look lookup listen on port and then your OS name using Google (or your other favorite search engine).

c) If nothing is listening any TCP ports that you check with a web based port checker, then TCP ports does not show up as open.

d) Be advised that you can not have two servers listening on the same the port on the same computer. So for example before you use an inbond-client side port checker you must make sure that uTorrent is not running - which explains on that they say

If uTorrent is currently open, you will need to completely close it at this time. Make sure that the green uTorrent icon is not still hiding in your notification area (next to your clock). If it is, right click on it and choose "Exit". Before moving forward to things like selecting torrents, seeders, and leachers, we need to verify that your port is open. We recommend downloading our free Open Port Check Tool to test if incoming connections are being allowed through your router on your uTorrent Listening Port

e) And generally if the program/app is running that you are trying to forward for, then the server is listening.

#8 Here are some catches about ping:

a) If the server that you forwarded requires that you reply to ping, well then you must enable responding to ping in the NAT router.

b) If the server that you forwarded does not require that you reply to ping, well that depends on another factor..

As to what that other factor is, I point to and quote the post by nwrickert (DSLR user #1070900) in DSLR ( Forums >Broadband Tech > Security > Security > DMZ and portforwarding are equally dangerous? on 2010-08-21 at 13:53:23.
While he tells people that responding to ping is dangerous, he replys to ping.

That's a pretty minor point. The reason some people prefer to not respond to ping, is to avoid demonstrating their presence on the net. Gibson has a public site whose presence on the net is well known, so that reason for not responding to ping simply does not apply.

While Steve Gibson does sometimes say some useful things, he mostly seems to be making mountains out of molehills

Note: Sorry for my misspelling, I meant replies.

c) There are certain troubleshooting tools that require that you reply to ping.

For example if you wanted to use the followings tool(s) at DSLR ( -> Tools: Smokeping, Line quality - Ping Test, and for 24x7 Line Monitoring...

d) If the ports are open (this means not just in the NAT router) but the program/app does not work: I have an odd feeling that with this server, you must reply to ping.


You must provide to users from the outside either your non bogan IP Address or DDNS.

What DNS is, here is the simple as possible version as how it works.

I know of a given domain name. What is their IP Address for that domain?

The first D in DDNS means/allows you to have a domain name the follows your non static non bogan IP Address. Which is a lot easier to provide and normally most people use DNS over the IP Address for the content servers that they want to connect to.. ;)
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Offline Greg67

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Hello PcWinTech and trpted,
Thankyou for your quick reply.

When I used the router's external IP in conjunction with the Remote Desktop Android (smart phone) program, I was able to remotely access the desktop PC.  However, if I try a port test with the SPF program, I still get the same error message "3389_TCP_Port In Use_Failed"!  This leaves me with a couple of questions:

(1) Is the port tester giving me a false negative?
(2) Should I make the external IP address static?
Once more, I  thankyou for your attention to this matter.
Yours Sincerely

Offline trpted

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The reason why that you got that error is because that client side inbound port checker is trying to check a port and that port is used by another program/app.

Since you know that Remote Desktop works:

a) More than likely that port is being used by that program/app.

b) Serious/odd question why do you need to use the client inbound port checker?


a) Yes I guess a false negative, as you can not have two servers on the same port listening at the same time. Either the inbound port checker or the program that you are trying to forward for (Remote Desktop in your case) is allowed to listen on that port.

b) Not required as you can use DDNS to find the machine.
« Last Edit: March 14, 2019, 06:19:10 AM by trpted »
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Offline Herentin

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I want to know more about this. It will make me get more and more back. Forums