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IMPORTANT PORT NUMBERS FOR THE LINUX SYSTEM ADMINISTRATOR Posted by Surendra Anne | May 19, 2011 | Interviews | 26 |

TA KE THIS C OU R SE Essentials of OpenStack Administration (LFS252)

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LINUX PORT NUMBERS This is bit important post on understanding the ports, their details and numbers.

A BOU T ME..!

My name is Surendra Kumar Anne. I

Some FAQ related PORTS

hail from Vijayawada which is cultural

Q. WHAT IS A PORT?

capital of south Indian state of

A port is piece of software which is used as docking point in your machine, where remote application can

Andhra Pradesh. I am a Linux

communicate. This is analogy to the physical ports for entering in to a country from different sea ports.

evangelist who believes in Hard work, A down to earth person, Likes to

Q. WHAT IS HARDWARE PORT?

share knowledge with others, Loves

This is a physical peripheral connecting point to a machine from a physical device.

dogs, Likes photography. At present I

Q. WHAT IS A SOCKET?

work at Bank of America as Sr.

Socket is combination of software Port and IP address.

You can contact me at surendra (@)

Q. WHAT IS THE RANGE OF PORTS OR HOW MANY PORTS ARE THERE?

linuxnix dot com.

Analyst Systems and Administration.

Port numbers can vary from 0 to 65535, so total we can get 65536 ports

Q. WHY PORT NUMBERS ARE JUST 65536? This is because limitation in TCP/IP stack where the port number field is just 16bit size. So we get only 2^16(2 to the power of 16) ports which are equal to 65536 available ports

Q. WHAT ARE THE WELL-KNOWN PORTS OR ASSIGNED PORTS OR DEFAULT PORTS? Well known ports are from 0 to 1023(total 2^10=1024 ports)

Q. WHAT DO YOU MEAN BY DEFAULT PORT? Default port is a designated port for particular well-known service such as web server, mail server, ftp server etc. By default FTP uses 21 port, DNS uses 53 and Apache uses 80 port.

Q. CAN WE CHANGE DEFAULT PORT FOR A SERVICE(EXAMPLE APACHE, SQUID)? Yes, we can change. In Apache and DNS we can change this using listen configuration entry in httpd.conf and named.conf. Squid have port entry in it’s squid.conf file to mention port number.

Q. WHAT ARE THE PROTOCOL NUMBERS FOR TCP AND UDP? Do not confuse this one with port numbers. TCP and UDP have their own numbers in TCP/IP stack. TCP protocol number: 6 UDP protocol number: 17

Q. IS THERE ANY WAY I CAN SEE ALL THE PORT INFORMATION IN LINUX? Yes, you can get that from /etc/services files.

Q. HOW CAN I SEE OPEN PORTS IN LINUX? Use nmap command.

WELL KNOWN PORTS 20 – FTP Data (For transferring FTP data) 21 – FTP Control (For starting FTP connection) 22 – SSH (For secure remote administration which uses SSL to encrypt the transmission) 23 – Telnet (For insecure remote administration) 25 – SMTP (Mail Transfer Agent for e-mail server such as SEND mail) 53 – DNS (Special service which uses both TCP and UDP) 67 – Bootp 68 – DHCP 69 – TFTP (Trivial file transfer protocol uses udp protocol for connection less transmission of data) 80 – HTTP/WWW(Apache) 88 – Kerberos 110 – POP3 (Mail delivery Agent) 123 – NTP (Network time protocol used for time syncing uses UDP protocol) 137 – NetBIOS (nmbd) 139 – SMB-Samba (smbd) 143 – IMAP 161 – SNMP (For network monitoring) 389 – LDAP (For centralized administration) 443 – HTTPS (HTTP+SSL for secure web access) 514 – Syslogd (udp port) 636 – ldaps (both ctp and udp) 873 – rsync 989 – FTPS-data 990 – FTPS 993 – IMAPS 1194 – openVPN 1812 – RADIUS 995 – POP3s 2049 – NFS (nfsd, rpc.nfsd, rpc, portmap) 2401 – CVS server 3306 – MySql 3690 – SVN 6000-6063-X11 Note 1: If protocol(TCP or UDP) is not mention then the above port are solely for TCP. Some service use UDP as mention in above list. Note 2: X11 use 6000 to 6063.. ports for connecting X11 from remote server. Post Views: 32

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SURENDRA ANNE Mr Surendra Anne is from Vijayawada, Andhra Pradesh, India. He is a Linux/Open source supporter who believes in Hard work, A down to earth person, Likes to share knowledge with others, Loves dogs, Likes photography. He works as Devops Engineer with Taggle systems, an IOT automatic water metering company, Sydney . You can contact him at surendra (@) linuxnix dot com.

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Join the discussion… Boy • 3 years ago

really useful, many thanks

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siddhu • 3 years ago

good and very use full and helpfull to me, thnk u

• Reply • Share ›

Poola Surendrareddy • 3 years ago

Very helpuful to me Surendra Brother........

• Reply • Share ›

KrishnaPriyanka Badam • 3 years ago

hi surendra, gud to met an AP guy,even i am from AP. I m recently joined as a trainee in the company on Linux based. Actually i am fed-up with this all.Could u please help me how can i understand the Socket programming nd all

• Reply • Share › Radnom

KrishnaPriyanka Badam • 3 years ago

WOW!! How about you actually use your brain instead of asking everyone for help.. You will fail in life and in your career path if this is how you approach a task,,, • Reply • Share ›



Mushthaq • 4 years ago

Great job Surendra.. Very helpful to me...... :)

• Reply • Share ›

ado • 5 years ago

really useful, many thanks

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isaurabhjha • 5 years ago

Great stuff and great job.

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dfd • 5 years ago

good

• Reply • Share ›

dhanraj • 5 years ago

U can update the common issue and troubleshooting steps which is helpful for beginners

• Reply • Share › Surendra Anne

dhanraj • 5 years ago

Do you mean issues with port?

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Revathi • 5 years ago

Good one. Very useful

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Vijay • 5 years ago

Nice blog...It's really helpful..thank you ...:-)

• Reply • Share › surendra Anne

Vijay • 5 years ago

Thanks vijay.. keep visiting it and inform to your friends about linuxnix.com. Please register your self for email updates from us here http://feedburner.google.c...

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venkatadry Mullapudi • 6 years ago

HI i am facing some problem many times in my environment some times the application team is not able to open the port and they say that it is the problem of the server my question is if application is started then only the port will open right? actually what can we check from server side to tell them that there is no problem with the server Thanks in Advance

• Reply • Share › Surendra

venkatadry Mullapudi • 6 years ago

Thats true.. when ever an application start which require network connection opens port. Trouble shooting the problem is bit combersum. Here are some points to check. 1)use nmap to check what ports are open in your system 2)Use tcpdump command to check how packets are going on?

• Reply • Share ›

jake66 • 6 years ago

HI i am facing some problem many times in my environment some times the application team is not able to open the port and they say that it is the problem of the server my question is if application is started then only the port will open right? actually what can we check from server side to tell them that there is no problem with the server Thanks in Advance

• Reply • Share › Surendra

Mod

jake66 • 6 years ago

Thats true.. when ever an application start which require network connection opens port. Trouble shooting the problem is bit combersum. Here are some points to check. 1)use nmap to check what ports are open in your system 2)Use tcpdump command to check how packets are going on?

• Reply • Share ›

Chandrasekhar • 6 years ago

Hi please update with protocols which they are using........

• Reply • Share › Surendra

Chandrasekhar • 6 years ago

Hi Chandra, all the above protocols uses TCP, the protocols which uses UDP is mention in note1 in this post..

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Chandrasekhar • 6 years ago

Hi please update with protocols which they are using........

• Reply • Share › Surendra

Mod

Chandrasekhar • 6 years ago

Hi Chandra, all the above protocols uses TCP, the protocols which uses UDP is mention in note1 in this post..

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Anand • 7 years ago

Hi, There is small typo mistake ...Please check once..Total No of ports should be 65536 but it mentioned as 35536...... Q. Why port numbers are just 65536? This is because limitation in TCP/IP stack where the port field is just 16bit size. So we get only 2^16 port which is equal to 35536 ports Regards, Anand

• Reply • Share › Surendra

Anand • 7 years ago

thanks for the hands-up.. updated the post..

• Reply • Share ›

Anand • 7 years ago

Hi, There is small typo mistake ...Please check once..Total No of ports should be 65536 but it mentioned as 35536...... Q. Why port numbers are just 65536? This is because limitation in TCP/IP stack where the port field is just 16bit size. So we get only 2^16 port which is equal to 35536 ports Regards, Anand

• Reply • Share › Surendra

Mod

Anand • 7 years ago

thanks for the hands-up.. updated the post..

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Chitta23m • 7 years ago

This is a Very useful Topic.Thank you so much Buddy.

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Himakumar2008 • 7 years ago

Thank you for detailed explanation ,

• Reply • Share ›

Chitta23m • 7 years ago

This is a Very useful Topic.Thank you so much Buddy.

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Himakumar2008 • 7 years ago

Thank you for detailed explanation ,

• Reply • Share ›

Kuldeep Sharma • 7 years ago

Very Nice... :))

• Reply • Share › Surendra

Kuldeep Sharma • 7 years ago

Thanks buddy..!

• Reply • Share ›

Kuldeep Sharma • 7 years ago

Very Nice... :))

• Reply • Share › Surendra

Mod

Kuldeep Sharma • 7 years ago

Thanks buddy..!

• Reply • Share › zaheer

Surendra • a year ago

Hello My Self Zaheer.I Have a doubt can windows user login in linux machine.If it is possible. Can u explain me.And Tell me Ur's Email-id.Reply me on my Eamil-d is [email protected] Thanks, zaheer.

• Reply • Share › Surendra

Mod

zaheer • 6 months ago

Yes, implement OpenLDAP or Samba PDC. 5

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Important Port numbers for the Linux system administrator - The Linux

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