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What is the use of each ports? is this the default port numbers?

Posted on 2008-06-12
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Last Modified: 2010-04-21
PORT     STATE SERVICE
22/tcp   open  ssh
25/tcp   open  smtp
80/tcp   open  http
111/tcp  open  rpcbind
443/tcp  open  https
631/tcp  open  ipp
878/tcp  open  unknown
5432/tcp open  postgres
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Question by:jaisonshereen
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by:kanalQko
kanalQko earned 100 total points
ID: 21768609
yes it is default ports but it doesnt mean that must be everytime used with this service or that the ssh service is still using only 22 port, it can be configured to any port for example 2222, but usuall are used standard reserved ports for some kind of services

ftp - 21
pop - 100
pop3 - 110
telnet - 23
ssh - 22
smtp - 25
http - 80
https - 443
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by:jaisonshereen
ID: 21768633
why we are using ports ? whats the use of each?
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by:Kent Olsen
ID: 21768777

Hi Jaison,

Here's a posted list of all of the well-known ports.  It's a lot more than you want to read, but the first couple of dozen will be names that you may recognize.  FTP, TELNET, SMTP (mail), SNTMP (network management), SSH, and others.

  http://www.iana.org/assignments/port-numbers

It might help to think of an IP addess as a phone number.  When you call corporate headquarters, someone nice office admin answers and asks you who you want to talk with or asks you for an extension.  The phone number gets you a switchboard, the extension gets you to a particular phone.

The IP address/Port number works the same way.  The IP address gets you to a server, the port number gets you to a particular service or application on the server.


Good Luck,
Kent
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Author Comment

by:jaisonshereen
ID: 21769281
ok..above all are tcp ports right? mostly we use only tcp ports ? whats the speciality of this ?

ftp - 21     -------- > this is for file transefer ..so file transfer through this port ..right?
pop - 100----------> i dont know
pop3 - 110 --------> for mails does mails comes through this? :-) whats the difference from above?
telnet - 23 ---------> for telnet sessions
ssh - 22 -----------> for ssh..secure transactions...but where we used this?
smtp - 25-----------> again for mail?
http - 80------------>  is this for website?
https - 443---------> website using secure protocol ... but what is the difference between ssh?

Please clarify my doubts!!

Thanks in advance!
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Kent Olsen earned 300 total points
ID: 21770106

ftp - 21     -------- > this is for file transefer ..so file transfer through this port ..right?

The FTP server listens for connections on port 21.  When an FTP client connects to the FTP server (on port 21) the two programs exchange whatever information that both programs understand.  They transfer files, perform simple queries like ls/dir (list files), cd (change directory), etc.

pop - 100----------> i dont know

I'm not sure where you read about POP and port 100.  I'm not aware of any well-known usage for port 100 today.

pop3 - 110 --------> for mails does mails comes through this? :-) whats the difference from above?

Yes -- POP3 (Post Office Protocol version 3) type mail is sent via port 110.

telnet - 23 ---------> for telnet sessions

Correct.

ssh - 22 -----------> for ssh..secure transactions...but where we used this?

To the user, SSH looks a lot like TELNET, but the data in encrypted and sent in coded form so that if someone were to monitor the data going over the network, all that they would see would be the encoded data, not something that they could easily read.

smtp - 25-----------> again for mail?

Yes.  It's another mail format.  

http - 80------------>  is this for website?

Yes.  By default, your web browser connects on port 80.

https - 443---------> website using secure protocol ... but what is the difference between ssh?

They're quite similar.  Both use a public/private key encryption mechanism that makes communication across the port as secure as technology allows.  There's a slight difference in handshake (the messages between the client and server) but perhaps the biggest difference is that an SSH connection is conversational, acting like a secure TELNET session.  HTTPS typically has a request from the client (browser) that is answered by the server and then the connection is terminated, acting like a secure HTTP session.


Kent
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Author Comment

by:jaisonshereen
ID: 21770250
thanks a lot of info..

is this comes in the category tcp ? why so ?

is there any other categorizes ? what is the specialty of tcp ?

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Expert Comment

by:Kent Olsen
ID: 21770601
Some ports will accept and communicate TCP sessions, some UDP sessions, others both.

There aren't a lot of differences between TDP and UDP, but the differences are significant.

The biggest difference is that packets sent over a TCP session are collected in the IP stack and passed to the application in the order that they were sent.  (It may be that a connection has about 15 routers between the client and server.  The packets don't all have to follow the same route, so it's possible that the can arrive out of order.  The TCP protocol requires that the packets be delivered in the correct order.)  UDP packets can arrive in any order.

TCP,  UDP, and ICMP are the 3 types of sessions that you're likely to see.  ICMP is how the network handles things like ping and traceroute.


Kent
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Author Comment

by:jaisonshereen
ID: 21771046
You mean this port will work in UDP also?

ftp - 21
pop - 100
pop3 - 110
telnet - 23
ssh - 22
smtp - 25
http - 80
https - 443


if no , which will work in UDP?
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Expert Comment

by:Kent Olsen
ID: 21771741

Any port can use TCP or UDP.  There's no limitation there.

The key element is to know which protocol (TCP, UDP) the server on a given port will connect.  Most servers will connect ONLY to TCP.  It makes no sense to have packets arrive out of order for FTP, SSH, TELNET, MAIL, etc. since the data would be all jumbled up.

For the list that you last posted, I believe that they will respond only to TCP connection requests.

Kent
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Assisted Solution

by:MicheleMarcon
MicheleMarcon earned 100 total points
ID: 21776308
All of these are "network protocols". The protocol is basically a set of rules. And a network protocol is a protocol that run in the network stack (i.e. it will make use of the lower levels protocols).

So for example "FTP" uses "TCP" for transmission on port "21".
"HTTP" uses "TCP" for transmission on port "80".

"DHCP" uses "UDP" for transmission on port "67".

And so on...
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