[Last Call] Learn about multicloud storage options and how to improve your company's cloud strategy. Register Now

x
?
Solved

Ftp high port

Posted on 2002-06-13
7
Medium Priority
?
352 Views
Last Modified: 2010-04-11
What is the ftp high-port ? Is it about ftp active and passive mode ?
0
Comment
Question by:rotaris357
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
7 Comments
 
LVL 3

Accepted Solution

by:
cincin77 earned 200 total points
ID: 7075261
Different from other TCP/IP applications, FTP uses 2 ports instead of one; one for control data and the other for the data. In normal operation; you open a connection to the port 21 of the ftp server.(this is the control connection) For this connection your local machine also has a port #.

The commands you enter like GET, PUT go through this channel. Aa the time comes to send or receive some data, FTP server opens a connection from its port # 20 to a local port in your machine which you sent to the server in advance through the control channel. This local port should be the 'high-port'.

However today most client machines are behind a firewall so it is not possible for the ftp server to open a connection to your machine. So your ftp client asks the server if it supports passive mode in which case the data connection is again opened by your client machine.

regards...
0
 
LVL 11

Expert Comment

by:geoffryn
ID: 7075728
Here is a great resource that explains FTP Active vs PASV in detail.

http://slacksite.com/other/ftp.html
0
 
LVL 16

Expert Comment

by:The--Captain
ID: 7084197
>However today most client machines are behind a firewall
>so it is not possible for the ftp server to
>open a connection to your machine

What kind of firewall are you using?  Mine certainly does do this (supports non-passive FTP) - it's called a stateful firewall, and any firewall that can't do it (these days) is basically crap (although most older firewalls *were* crap, and couldn't do it, hence passive FTP)

Otherwise, all the info I see here seems good, particularly geoffryn's URL - I vote for his answer...

Cheers,
-Jon


0
Looking for the Wi-Fi vendor that's right for you?

We know how difficult it can be to evaluate Wi-Fi vendors, so we created this helpful Wi-Fi Buyer's Guide to help you find the Wi-Fi vendor that's right for your business! Download the guide and get started on our checklist today!

 
LVL 3

Expert Comment

by:cincin77
ID: 7085821
It is not a good idea to allow incoming tcp connection requests.
it can be compromised.
0
 
LVL 16

Expert Comment

by:The--Captain
ID: 7091048
>It is not a good idea to allow incoming tcp connection
>requests. it can be compromised.

Please refer to the CERT ID that indicates such vulnerabilities in iptables (I would also be interested in *any* CERT advisory regarding a stateful firewall).

Cheers,
-Jon
0
 

Author Comment

by:rotaris357
ID: 7101463
Thanks Cincin77 and geoffryn that make me clear , but I choose Cincin77 because he answers the question with his intention , and I think he can make me clear in the short of the detail.
0
 
LVL 16

Expert Comment

by:The--Captain
ID: 7103275
Whatever works...

Cheers,
-Jon
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

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

What monsters are hiding in your child's room? In this article I will share with you a tech horror story that could happen to anyone, along with some tips on how you can prevent it from happening to you.
It’s time for spooky stories and consuming way too much sugar, including the many treats we’ve whipped for you in the world of tech. Check it out!
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…
In a question here at Experts Exchange (https://www.experts-exchange.com/questions/29062564/Adobe-acrobat-reader-DC.html), a member asked how to create a signature in Adobe Acrobat Reader DC (the free Reader product, not the paid, full Acrobat produ…

656 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