Regex to validate port number

Question

I'm using this regex (6553[0-5]|655[0-2]\d|65[0-4]\d{2}|6[0-4]\d{3}|[1-5]\d{4}|[1-9]\d{0,3} to validate port numbers. Somehow this is not working. What is wrong with this? Can anybody point me out.

What are you trying to do? Maybe post some unit test code that is failing or something? — Bob Kuhar
– Bob Kuhar, Commented Oct 19, 2012 at 5:51
what port numbers do you want 2 validate..are they in specific range or do u want it 2 just validate — Anirudha
– Anirudha, Commented Oct 19, 2012 at 6:24
@Fake.It.Til.U.Make.It I just want to validate from 1 to 65535. — Soham Dasgupta
– Soham Dasgupta, Commented Oct 26, 2012 at 11:03
@SohamDasgupta no need to use regex here..just parse the number to int and then check if it is in required range! — Anirudha
– Anirudha, Commented Oct 26, 2012 at 12:58

Pavan Kumar · Accepted Answer · 2022-02-02 10:05:27Z

59

What exactly do you mean by not working?

You could try something like so: ^([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$ (obtained from here).

This will make sure that any given string is numeric and between the range of 0 and 65535.

Assuming your regular expression matches the same range, it is missing the start and end anchors (^ and $ respectively), so it would allow other strings besides the actual port.

Update 2 Feb 2022: Fixed the regex to reject values like 00 etc. The updated regex is sourced from the comment below. This regex can be better understood and visualized here: https://www.debuggex.com/r/jjEFZZQ34aPvCBMA

edited Feb 2, 2022 at 10:05

Pavan Kumar

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answered Oct 19, 2012 at 5:51

npinti

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5 Comments

Soham Dasgupta Over a year ago

I'm using DexExpress textbox and using this regex as mask. But at runtime its generating an error saying incorrect syntax.

npinti Over a year ago

@SohamDasgupta: Maybe you need to put everything between quotation marks? Maybe looking at the documentation will help.

Soham Dasgupta Over a year ago

Putting qoutes is something I learned 10yrs back when I started programming. Anyway thanks.

elfan Over a year ago

The first part ([0-9]{1,4}) is incorrectly allowing 0000. It should be [1-9]\\d{0,3}|0

saber tabatabaee yazdi Over a year ago

Hi, @elfan that accept 00 or 000 or 0000 I find accidentally this entry and realized there is a little mistake in the pattern: "After correction of your regexp : Port = '([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-3][0-9]|6553[0-5])'; // 1..65535" This Pattern is allowed for the range between 1-65539, it should be: Port = '([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])'; // 1..65535 github.com/findhit/proxywrap/issues/13

chtimi59 · Accepted Answer · 2019-01-30 16:19:44Z

15

When, we search "how to validate port number" on Google we unfortunately land here

However (except if you have really no other choice...),

Regex is clearly not the way to validate a port number !

"One" (slightly better) way may be:

step 1: Convert your string into number, and return FALSE if it fails
step 2: return TRUE if your number is in [1-65535] range, and FALSE otherwise

Various reasons, why Regex is not the right way ?

Code readability (would takes few minutes to understand)
Code robustness (there are various ways to introduce a typo, a unitary test would be required)
Code flexibility (what if port number can be extended to a 64-bits number !?)
etc. ...

answered Jan 30, 2019 at 16:19

chtimi59

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1 Comment

RBT Over a year ago

Good suggestion. For step 1,we can use System.UInt16.Tryparse(string value, out int result). Although UInt16 range includes zero as well which is not a valid port number.

wski · Accepted Answer · 2019-11-13 21:53:13Z

Here is the example I'm using to validate port settings for a firewall. The original answer will match 2 strings. I can only have 1 string match.

(6553[0-5]|655[0-2][0-9]|65[0-4][0-9][0-9]|6[0-4][0-9][0-9][0-9][0-9]|[1-5](\d){4}|[1-9](\d){0,3})

To get: 22,24:100,333,678,100:65535 my full validation (That will only return 1 match) is

(6553[0-5]|655[0-2][0-9]|65[0-4][0-9][0-9]|6[0-4][0-9][0-9][0-9][0-9]|[1-5](\d){4}|[0-9](\d){0,3})(:(6553[0-5]|655[0-2][0-9]|65[0-4][0-9][0-9]|6[0-4][0-9][0-9][0-9][0-9]|[1-5](\d){4}|[0-9](\d){0,3}))?(,(6553[0-5]|655[0-2][0-9]|65[0-4][0-9][0-9]|6[0-4][0-9][0-9][0-9][0-9]|[1-5](\d){4}|[0-9](\d){0,3}){1}(:(6553[0-5]|655[0-2][0-9]|65[0-4][0-9][0-9]|6[0-4][0-9][0-9][0-9][0-9]|[1-5](\d){4}|[0-9](\d){0,3}))?)*

hinekyle · Accepted Answer · 2013-05-02 19:42:57Z

3

Number() is the function you want "123a" returns NAN

parseInt() truncates trailing letters "123a" returns 123

<input type="text" id="txtFld" onblur="if(Number(this.value)>0 && Number(this.value)<65536){alert('valid port number');}" />

jsfiddle

answered May 2, 2013 at 19:42

hinekyle

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1 Comment

Mohsen Kamrani Over a year ago

Too late :) , but this is obviously wrong. You can test it with "2e2" for example.

Antonio · Accepted Answer · 2015-05-18 12:15:20Z

2

A more strict approach is to have a regex matching all numbers up to 5 digits with the following string:

*(^[1-9]{1}$|^[0-9]{2,4}$|^[0-9]{3,4}$|^[1-5]{1}[0-9]{1}[0-9]{1}[0-9]{1}[0-9]{1}$|^[1-6]{1}[0-4]{1}[0-9]{1}[0-9]{1}[0-9]{1}$|^[1-6]{1}[0-5]{1}[0-4]{1}[0-9]{1}[0-9]{1}$|^[1-6]{1}[0-5]{1}[0-5]{1}[0-3]{1}[0-5]{1}$)*

edited May 18, 2015 at 12:15

Antonio

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answered May 18, 2015 at 11:55

jjluke

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Comments

Bugs · Accepted Answer · 2017-05-26 09:58:47Z

2

"^((6553[0-5])|(655[0-2][0-9])|(65[0-4][0-9]{2})|(6[0-4][0-9]{3})|([1-5][0-9]{4})|([0-5]{0,5})|([0-9]{1,4}))$"

It will allow everything between 0-65535 inclusive.

edited May 26, 2017 at 9:58

Bugs

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answered Dec 29, 2016 at 0:18

anon

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Comments

saber tabatabaee yazdi · Accepted Answer · 2018-07-12 14:20:53Z

2

Here is single port regex validation that excludes ports that start with 0

^([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])

Here is validation for port range (ex. 1111-1111)

^([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])(-([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5]))?$

link:

https://github.com/findhit/proxywrap/issues/13

edited Jul 12, 2018 at 14:20

saber tabatabaee yazdi

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answered Oct 24, 2016 at 8:19

lavaGolem

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Comments

Teo · Accepted Answer · 2021-05-21 13:00:23Z

2

Landed here as well, searching specifically for REGEX to validate port number. I see the approved solution was not fixed yet to cover all scenarios ( eg: 007 port, and others ) and solutions from other sites not updated either (eg).

Reached same minimal solution as saber tabatabaee yazdi, that should cover the 1-65535 range properly:

^([1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$

Enjoy !

edited May 21, 2021 at 13:00

answered May 21, 2021 at 11:58

Teo

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Comments

Soham Dasgupta · Accepted Answer · 2021-07-29 07:19:12Z

2

^((6553[0-5])|(655[0-2][0-9])|(65[0-4][0-9]{2})|(6[0-4][0-9]{3})|([1-5][0-9]{4})|([0-5]{0,5})|([0][0-9]{1,4})|([0-9]{1,4}))$

I have tested above regrex with Junit run the for loop from 0-65535

Ex: 00001 - 65535 with leading Zeros 1 - 65535 without leading Zeros Ex:====

(6553[0-5]) : 65530-65535
(655[0-2][0-9]) : 65500-65529
(65[0-4][0-9]{2}): 65000-65499
(6[0-4][0-9]{3}) : 60000-64999
([1-5][0-9]{4}) : 10000-59999
([0-5]{0,5}) : 00000-55555 (for leading Zeros)
([0][0-9]{1,4}) : 00000-09999 (for leading Zeros)
([0-9]{1,4}) : 0000-9999 (for leading Zeros)

edited Jul 29, 2021 at 7:19

Soham Dasgupta

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answered Jul 29, 2021 at 1:15

Neeraj Singh Dhapola

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Comments

Leon Adler · Accepted Answer · 2016-02-04 23:11:24Z

1

The accpeted answer by npinti is not right. It will not allow to enter port number 1000, for example. For me, this one (not nice, I'm a beginner) works correctly:

/^((((([1-9])|([1-9][0-9])|([1-9][0-9][0-9])|([1-9][0-9][0-9][0-9])|([1-6][0-5][0-5][0-3][0-5])))))$/

edited Feb 4, 2016 at 23:11

Leon Adler

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answered Feb 4, 2016 at 22:17

R-Man Growduino

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Comments

Shane Rowatt · Accepted Answer · 2016-06-15 03:37:40Z

1

@npinti 's answer allows leading zeros in the port number and also port 0 means pick any available port so I would exclude that so the regex becomes

^([1-9][0-9]{0,4}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$

If you want to allow port 0 then

^(0|[1-9][0-9]{0,4}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$

answered Jun 15, 2016 at 3:37

Shane Rowatt

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2 Comments

daniel.caspers Over a year ago

I really like the intent of this answer as I have the exact same problem right now. Notice that your main difference is that the first capture group allows [1-9][0-9]{0,4}, but this means numbers like 99999 can get in, which violates the question. I'll keep trying to see if I can find a correction for this.

daniel.caspers Over a year ago

I think you meant to use [1-9][0-9]{0,3} instead? This will cover 1-9999 inclusive, but disallow leading zeroes.

Bugs · Accepted Answer · 2017-05-26 09:58:17Z

1

The solution:

Dim Minlenght As Integer = 1
Dim Maxlenght As Integer = 65536

Regex.IsMatch(sInput,"(^\d{0},{1}$)", "{" + Minlenght, Maxlenght + "}")

edited May 26, 2017 at 9:58

Bugs

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answered May 26, 2017 at 9:56

Andrea Casagrande

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Comments

NOYB · Accepted Answer · 2020-09-05 23:47:32Z

1

If variable is an integer between 1 and 65536 (inclusive) then...

if [[ "$port" =~ ^[0-9]+$ && $port -ge 1 && $port -le 65536 ]]; then

answered Sep 5, 2020 at 23:47

NOYB

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