Solved

changing the listening ports affects what ...

Posted on 2004-09-04
4
195 Views
Last Modified: 2010-04-19
to be able to cross a firewall to connect to my server at home
i had to change the port number for remote desktop RDP from 3389 to 110 in the registry
an i can remote desktop now to my server

110 is also used by pop3, and i use it now also for RDP now

will this have an influence on pop3

so my question is:

when 2 programs listen to the same port, will this not cause some trouble to those programs and if yes, where

tks a lot
karel
0
Comment
Question by:karel_jespers
  • 2
  • 2
4 Comments
 
LVL 34

Accepted Solution

by:
Dave_Dietz earned 450 total points
ID: 11981679
Yes, this has the potential to cause a problem if you try to run two programs on the same machine that *listen* on the same port.  Unless you are running a POP3 *server* on your machine it shouldn't matter if you set up a different program to use that port for incoming connections.

As an example, there is a (not very popular) chat server that binds to port 443 for clients to connect to.  443 is the standard port used for SSL Web traffic and this causes a problem when you try to use SSL for a webserver on the same machine because both of the programs want to use port 443 exclusively.  Generally the first program to bind a prot wins and any other programs will generally pop up some sort of error about not being able to bind to a specific port.

Some programs are configurable to bind to a given port but only on a certain IP interface which can allow youto run different programs using the same port as long as they will both use a different IP address.

Once again, as long as you only have one program (RDP) that is listening on (binding) a port for exclusinve use you shouldn't have any problems.

Side question: is there any reason you didn't simply open up port 3389 for RDP traffic?

Dave Dietz

Dave Dietz
0
 
LVL 6

Author Comment

by:karel_jespers
ID: 11983432

is there any reason you didn't simply open up port 3389 for RDP traffic?
----------------------------------------------------------------------------------
to be able to cross a firewall
x  ==> firewall ==> homeserver
i have the permissions of the networkadministrator to run everything i want on port 110
but he doesn't want to open de port 3389 on his firewall
so i had to change the listening port

tks dave

for those programs who's ip adress can be configure:
can i then do the following

1) i configure my only networkinterface on my server with 2 ipadresses
2) i configure both program 1 and program 2 to listen to port eg 110
3) on my router i route program1 (port eg 110) communication to networkaddress 1
4) on my router i route program2 (port eg 110) communication to networkaddress 2

can you give me an example or links of such a programs who's listening port + ip adress can be configured (bcs i want to do some testing)

tks karel

 
0
 
LVL 34

Expert Comment

by:Dave_Dietz
ID: 11985027
If your network admin won't open port 3389 I guess that's a good reason to use a different port.....  :-)

1) You can bind as many IP addresses to your NIC as you want as long as you aren't using DHCP to have a dynamic address assigned to you.

2) Yes, on different IPs

3 and 4) generally the way a router/NAT device works is to take any packets arriving at port x on the router/NAT and forward them to port y on the specified internal IP address.  Unless you have a router/NAT with some very advanced features it won't be able to send packets arriving on port 110 to different destination addresses based on what protocol (POP3 vs. RDP) the incoming packets are using.

It sounds like your admin doesn't want to open any non-standard ports.  Might try asking if he (she) will open one or more of the following and then use them as you feel fit:

20   - FTP-data
21   - FTP
25   - SMTP
80   - HTTP
119 - NNTP
443 - HTTPS (SSL)

Dave Dietz
0
 
LVL 6

Author Comment

by:karel_jespers
ID: 11985158
tks a lot for your help
karel
0

Featured Post

Courses: Start Training Online With Pros, Today

Brush up on the basics or master the advanced techniques required to earn essential industry certifications, with Courses. Enroll in a course and start learning today. Training topics range from Android App Dev to the Xen Virtualization Platform.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

I've always wanted to allow a user to have a printer no matter where they login. The steps below will show you how to achieve just that. In this Article I'll show how to deploy printers automatically with group policy and then using security fil…
While rebooting windows server 2003 server , it's showing "active directory rebuilding indices please wait" at startup. It took a little while for this process to complete and once we logged on not all the services were started so another reboot is …
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …
A short tutorial showing how to set up an email signature in Outlook on the Web (previously known as OWA). For free email signatures designs, visit https://www.mail-signatures.com/articles/signature-templates/?sts=6651 If you want to manage em…

776 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question