How to open and close port in Linux?

DaRecordon · May 20, 2017

I want to open or close a port in linux which is in listening mode between my client and server application. Is there any manual command line option in Linux to close or open a port? btw, how to check a port is being opened/closed or not? many thanks!

racksandcloud · May 20, 2017

You can use the below command to find which all ports are listening.

netstat -lntup

-p = name of the program
-t = tcp ports
-u = udp ports
-l = only services which are listening on some port
-n = show port number, don't try to resolve the service namerewall

If you wants to open an incoming TCP port in Linux iptables firewall,

iptables -I INPUT -p tcp --dport 5555 --syn -j ACCEPT

If you want to open a UDP port

iptables -I INPUT -p udp --dport 5555 -j ACCEPT

service iptables save

for blocking a port

iptables -A OUTPUT -p tcp --dport 5555 -j DROP

LJSHost · May 26, 2017

0.0.0.0:22 <-------
127.0.0.1:25 <--------

22 and 25 are the ports

hostmeja · May 26, 2017

I recommend getting ConfigServer Security & Firewall or a firewall tool with UI to better assist you. In most cases they can advise what port to close and a simple UI to turn it off /on.

qbeststar · May 26, 2017

DaRecordon said:
how to check a port is being opened/closed or not? many thanks!

Hi, for example

netstat -anp | grep 22 or lsof -i | grep 22

or you can use this website http://ping.eu/port-chk/ put your ip and port.

AlphaNine Vini · May 26, 2017

You need to use the iptables or a firewall that can enable you to block any port for the users.

Block port 80:
iptables -A INPUT -p tcp --dport 80 -j ACCEPT

Block a IP address:
iptables -I INPUT -p tcp -s 103.18.45.18 -j DROP

How to open and close port in Linux?

DaRecordon

Well-known member

racksandcloud

Well-known member

djsmiley2k

Well-known member

AlbaHost

Well-known member

LJSHost

Well-known member

DaRecordon

Well-known member

Kaz Wolfe

Well-known member

LJSHost

Well-known member

Kaz Wolfe

Well-known member

LJSHost

Well-known member

hostmeja

Member

qbeststar

Well-known member

AlphaNine Vini

Member

Latest posts New threads

Latest posts

New threads

Latest Hosting Offers New Reviews

Latest hosting offers

Popular Contributors - Past 30 Days

Sponsors

Tag Cloud