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Listening on port 55550

Posted on 2015-02-07
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Last Modified: 2015-02-12
I have received a simple server python script from a contract developer that I am trying to set up on a local computer for testing. The script is set up to listen on port 55550 which I am having trouble with. I have attempted to set up port forwarding on my linksys router but every time I attempt to test with the script I get an error associated with port 55550. I have tried running port scanners against my internet IP address but I cannot find any open reports. I assume my ISP blocks port scanning at the service level because every port I scan fails.

What I am trying to figure out is whether or not port 55550 has access through my ISP, if not I need to find an alternate port that I can modify the python script to listen on. The python script is listening for a REST protocol communication from a mobile device that is outside my local network that the script is running on.

How do I figure out if port 55550 is available through my ISP? If this port is not an option because of some restriction my ISP has established, how do I find other open ports that I can use?

My ISP is Windstream DSL. I have tried to find information on their technical pages but have had zero luck. I had even less luck speaking with someone in their technical support center.
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Question by:gacto
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Expert Comment

by:Predrag Jovic
ID: 40595674
It is not usual that ISP blocks all ports, so most likely that your router have port 55550 closed.
How do I figure out if port 55550 is available through my ISP?
Easiest way to test this is to have another router (in case that your router is not adsl router) and spare PC. Then you can connect from PC connected  second router to your current router and test WAN connection of that router on port 55550. This eliminate possibility that your ISP is blocking your port.
If script works - port is blocked by ISP. If script don't work, port is not properly forwarded.

Method that don't eliminate completely (but can be used with adsl) ISP is to use demilitarized zone (DMZ).. put PC in DMZ of your router, and enable DMZ. All ports should be automatically redirected to PC in DMZ.
This method - if script works - port for 5550 was closed.
But in case that script don't work - maybe DMZ is not configured properly or ISP is blocking your port.

And probably you need to add exception to rules in your firewall (or easiest way to test is to temporary turn off firewall).
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Author Comment

by:gacto
ID: 40595717
Predrag,

Can you provide more detail about how to accomplish the first suggestion? I would like to determine the root cause of this problem before I switch over to DMZ. The option for DMZ may be the better long term option since I will likely be running this server for testing for quite a while.

The current router that I am trying to configure is not an ADSL router. I am using the ADSL router in Bridge Mode so the only function it provides is as a modem.

"PC Connected to second router to your current router" - should this be a PC connected to a network outside my home network? If I am setting them up on the same network won't I have DHCP clashes?

"test WAN connection of that router on port 55550" - this is a deeper level of network testing than I have performed before so I am not sure what steps are involved.

Scott
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Accepted Solution

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Predrag Jovic earned 500 total points
ID: 40595756
You can set Router 1 in address range 192.168.0.0/24 (or any other)
Connect PC 1 to  LAN on Router1 (Router1 - IP range)
Connect Router 1 LAN to WAN of Router 2
Add to WAN static IP address (or get one from DHCP server on Router 1), but you need to know what address is to test script.
Router2 needs to be in different IP range (like 192.168.1.0/24 - or any other).
PC that you need to test connect to Router2 LAN ports (Router2 - IP range).
And you are ready to test - from PC1 to PC2.

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Author Comment

by:gacto
ID: 40595793
ok that makes sense and i have plenty of hardware to set this up.

to test between the two PCs I assume pinging from one PC to the other over port 55550 will yield the results I am looking for?
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Expert Comment

by:Predrag Jovic
ID: 40595801
Yes - if you test from PC on Router1.
That's testing all devices on your side (port, firewall) since you are testing over WAN port.
If you make it work in that environment, it will work over the internet if your ISP don't block ports (or your dsl router).
:)
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Author Comment

by:gacto
ID: 40595804
got it. i will post results shortly.
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Expert Comment

by:Predrag Jovic
ID: 40595806
And you can't ping port 5550 - but you can use telnet .
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Author Comment

by:gacto
ID: 40595855
I am having trouble getting the routers linked together. I have connected them as per your diagram, set up router 2 with a static IP, assigned a new address range for DHCP on router 2. But I must have something set wrong. I cannot get router 2 to show up in the DHCP table of router one. Router 1 Network is set as 192.168.1.1. Here is what I have done for setup on router 2:

Internet Connection Type: Static IP

Inter IP Address: 192.168.1.150
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.1.1
DNS 1: 192.168.1.1

Network Setup
Router IP Address: 192.168.0.50
Subnet Mask: 255.255.255.0

DHCP Server: Enabled
Start IP Address: 192.168.0.100

What am I doing wrong in the configuration?
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Author Comment

by:gacto
ID: 40595909
I have also tried to setup router 2 as an automatic configuration - DHCP with no luck either.
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Author Comment

by:gacto
ID: 40595941
Predrag,

Disregard the last two posts. User error...

Now that I have the two routers hooked up correctly I can ping from the PC connected to the second router to all IP ranges on router 1. But I cannot ping from any of the PCs connected to router 1 to the PC connected to router to. Telnet does not work in either direction.

Here is the configuration I have now just to be certain I am going in the right direction.

Primary router (router 1) - IP Address: 192.168.1.1, port forwarding setup for port range 55550-55550 to direct to 192.168.1.113 - this is the PC that is running the Python script

Secondary router (router 2) - Internet setup is Automatic Configuration - DHCP, Network Setup IP Address: 192.168.0.50, PC connected to router 2 has static IP 192.168.0.101

I can ping from 192.168.0.101 to all 192.168.1.* IP addresses. I cannot telnet to any IP on the 192.168.1.* network.

I cannot ping nor can I telnet from 192.168.1.* to any IP address on 192.168.0.*
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Author Comment

by:gacto
ID: 40595946
minor correction, I can telnet from 192.168.0.101 to 192.168.1.1 over port 80. I cannot telnet to anything in the DHCP range of 192.168.100-149.
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Expert Comment

by:Predrag Jovic
ID: 40595947
Try to put PC2 in DMZ on Router 2.
Direction from PC2 to P! is not important in your case (I guess).
Telnet should not work on port 5550, but you should see that connection will be opened, and after will be close due to inactivity....

Routers can also have their own firewall...
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Author Comment

by:gacto
ID: 40595960
I have the firewall on router 2 disabled to eliminate that as a problem.

I have put PC2 in DMZ on router 2 but I still cannot access PC2 from PC1 through either ping or telnet. I don't know what else to try at this point.
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Expert Comment

by:Predrag Jovic
ID: 40595963
You need to test PC2 behind WAN (I guess).
You don't need to try to connect to that PC directly (your first router have no idea that 192.168.0.0/24 network even exist).
You need to connect to WAN port of router 2 (192.168.0.50 - if I understood well).
Router 2 needs to be configured to redirect traffic to PC (that's Port Forwarding).

If you use DMZ, all traffic that is intended for router's WAN port is redirected to PC in DMZ.
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Author Comment

by:gacto
ID: 40595974
ok that is how i thought i had this configured. i don't understand what you are suggesting that i do now.
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Expert Comment

by:Predrag Jovic
ID: 40595975
So, you don't need to reach PC2, you need to make router send traffic that is targeting WAN port redirect to PC2.
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Expert Comment

by:Predrag Jovic
ID: 40595979
What is model of your Router2?

And send me screenshoot of your WAN port on Router2. (If that is router that have PC behind WAN port).
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Expert Comment

by:Predrag Jovic
ID: 40596013
It's late here where I am.
I can point you to Port Forward, for some help.
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Author Comment

by:gacto
ID: 40596054
i am out for the next few hours also. i will keep working and post updates. thanks for the help so far.
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Author Comment

by:gacto
ID: 40596084
Ok I just got it working. The WAN port on router 2 was assigned 192.168.1.147 as an IP address. I was able to forward all traffic to the PC and verify that all ports are working and traffic is flowing correctly.

In the meantime I was also able to locate an error in the installation of the latest version of Python which I installed. Now that I have updated that installation without the error, I was able to get the script running correctly and have been able to communicate from the mobile app to the server side application over port 55550.

Thanks for the help, and for your patience, in troubleshooting this issue.

Scott
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Expert Comment

by:Predrag Jovic
ID: 40596722
You are welcome.
I am glad that I could help you. :)
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Author Closing Comment

by:gacto
ID: 40606288
Preheat,

Sorry for the delay in awarding the points, I thought I had already closed this out. Thanks again for your help.

Scott
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Expert Comment

by:Predrag Jovic
ID: 40606427
No problem. :)
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