How do I check if a port is open

svgnamy

I am installing ssl certificates on a few of my vps. I've already installed two and everything works great. those vps are on debian. I have a vps on centos but when I install the ssl and test it, I get a 102 connection error in chrome.

I think my configuration is correct, but I want to see if the ssl port is open. the tool I found on Google says port 80 was closed so I figured I couldn't trust it.

anyone know how I can check if a port is open?

jarland

netstat is your best friend :)

luxor

When can't test them directly from any of my other machines (telnet, hping3, nc, etc.) I use the online check of Gibson Research, ShieldsUP!

There you can test directly common ports or custom groups of ports also. It's quite handy.

Edit: Oh! If you get a 102 error then I think that should be open since a 1xx error is informational, but jarland is right that netstat -ln is your command. But don't forget the firewall. ;)

risharde

Try my simple port check tool, SSL or in this case HTTPS I think would be port 443 http://www.risharde.com/portcheckutility.html You'll have to visit the website while on the VPS you want to check btw. Good luck

Damian

netstat -ln. If it shows up in the list, something is accepting connections for it.

You can grep for your :portnumber too, if you have a lot of connections open.

cosmicgate

Netstat -ln | grep portno

rsk

the good old way, telnet :)

telnet [ip of host] [port]

in cmd

But if you want to see from the vps/server itself, then ye netstat is your friend.

regards, R. Alkhaili

fresher_06

telnet targetipadddress 443 .. (443 is the default port for SSL) from ur source machine

If u get something like escape character .. it means your SSL port is open.. however if it says connecting .. for long time . it means SSL port is closed

miTgiB

lsof -i:port number

nunim

nmap -p xx hostname

nunim@numdesk:~$ nmap -p 80 google.com

Starting Nmap 5.21 ( http://nmap.org ) at 2012-10-14 22:18 EDT
Nmap scan report for google.com (74.125.227.130)
Host is up (0.059s latency).
Hostname google.com resolves to 11 IPs. Only scanned 74.125.227.130
rDNS record for 74.125.227.130: dfw06s17-in-f2.1e100.net
PORT   STATE SERVICE
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.36 seconds

svgnamy

great thanks. nmap worked. It shows the port as closed. I don't know how to open it. My firewall (iptables has been stopped) I'm wondering how to open a port that I didn't close. I'm using centos with lnmp installation script.

Does anyone know how to open the port?

Breezehost

To open port via iptables you can use the command as :-

iptables -I INPUT -p tcp --dport 25 -j ACCEPT

iptables -I OUTPUT -p tcp --dport 25 -j ACCEPT

/etc/init.d/iptables save

/etc/init.d/iptables restart