Port is a generic term that can refer to port number (software related term), and computer hardware port. Here, questions referencing this tag refer to port numbers.

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43
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11answers
6k views

Does changing default port number actually increase security?

I have seen advice saying you should use different port numbers for private applications (e.g. intranet, private database, anything that no outsider will use). I am not entirely convinced that can ...
43
votes
5answers
286k views

How to check if a port is blocked on Windows?

What is the easiest way to check if port 3306 on my localhost is being blocked?
28
votes
16answers
28k views

Why Block Port 22 Outbound?

I'm a programmer, and I have worked for a few clients whose networks block outgoing connections on port 22. Considering that programmers often need to use port 22 for ssh, this seems like a ...
28
votes
4answers
10k views

Bind to ports less than 1024 without root access

I would like to run applications I'm working on that binds to port numbers less than 1000 without requiring root access. I'm using Linux Mint and have root access to set it up. I would ideally like ...
23
votes
9answers
51k views

How do I find out whether a port is available on Ubuntu 8.04?

Is there any command I can run from bash that will tell me whether a port is already open?
19
votes
3answers
35k views

How do you free up a port being held open by dead process?

A colleague of mine recently ran into a problem where a process that had supposedly died was still bound to a network port, preventing other processes from binding to that port. Specifically, netstat ...
18
votes
9answers
122k views

Check if port is open or closed on a Linux server using SSH?

How can I check if a port is open or closed on a Linux server (running Cent OS 5 and cPanel) using SSH? EDIT: And how can I open the port if it is closed? Thanks, James
17
votes
6answers
88k views

What firewall ports do I need to open when using FTPS?

I need to access an ftps server (vsftpd) on a vendor's site. The vendor has a firewall in front of the ftps server and I have a firewall in front of my ftps client. I understand that ports 990, 991 ...
16
votes
2answers
20k views

What is the maximum port number?

I'd like to set some linux services to non-standard ports - what's the highest valid port number?
15
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7answers
42k views

How to check if a port is open for remote system(ubuntu)

Is it possible to check that if the ports are open for the remote system on ubuntu server? I should able to check if a port(eg:ssh) on my machine is open for the remote machine.
15
votes
4answers
6k views

Change protocol associated with port in wireshark

I'm trying to monitor some web traffic using wireshark. Our web proxy is on port 9191. How can I get the wireshark view to treat port 9191 just like port 80 - ie as HTTP. Just using Decode_As on the ...
15
votes
1answer
24k views

What ports to open for mail server?

I have just finished setting up a Postfix mail server on a linux (ubuntu) platform. I have it sending and receiving email and it is not an open relay. It also supports secure smtp and imap. Now this ...
15
votes
6answers
9k views

Is there an equivalent to ssh-copy-id for Windows?

Is there any equivalent or port of ssh-copy-id available for Windows? That is, is there an easy way to transfer SSH keys from a local machine to a remote server under Windows? In case it helps, I'm ...
14
votes
9answers
111k views

Disable TeamViewer from “stealing” Port 80?

How can you disable TeamViewer from using/reserving port 80? I am certain in the previous version <v4.1.6 there used to be a radio button option in "options" which disabled it from needing it, but ...
14
votes
4answers
17k views

What firewall ports need to be open to allow access to external git repositories?

What firewall port(s) need to be open to allow access to external git repositories?
13
votes
5answers
6k views

Understanding Ports: How do multiple browser tabs communicate at the same time? [closed]

I realized today that I fundamentally don't understand how port communication works. If I fire up an instance of a webserver listening on port 80, it can respond to many requests from many different ...
13
votes
10answers
137k views

How can I find out if a port is opened or not?

I have installed Apache server on my Windows 7 computer. I was able to display the default index.php by typing http://localhost/ in the address line of my browser. However, I am still unable to see ...
13
votes
2answers
659 views

How should I select the port number for a new tool?

I'm creating an internal collaboration tool that will use a central server (on an intranet) and one or more ports for socket communication to clients. I know that many ports are reserved for ...
13
votes
2answers
407 views

Ethernet port plastic plug blocking port access on server

I have Dell Poweredge server with plastic blockers inside their ethernet ports. My problem is that I don't know how to take it out. You can see photo of the plug here: I tried to pull them out, or ...
11
votes
4answers
12k views

How to allow non-root user to listen on privileged port?

I want syslog to run as a non-root user on my linux box. That makes it impossible for it to bind to port 514 - because that's a privileged port. Is there any way I can grant non-admin user "foo" the ...
10
votes
4answers
20k views

How do I see if a port is in use on a windows machine?

I am using Windows XP pro, and I need to know if something is registered on a port. If so how can I tell what is on the port? EDIT What I mean by registered is that I am trying to test a .NET ...
9
votes
3answers
267 views

advantages in closing a port where no services are running

Are there advantages in closing a port where no services are running? What do I gain in terminating a connection at iptables level instead of what does it next (I guess OS).
9
votes
7answers
28k views

How do I get rid of sockets in FIN_WAIT1 state?

I have a port that is blocked by a process I needed to kill. (a little telnet daemon that crashed) The process was killed successfully but the port is still in a 'FIN_WAIT1' state. It doesn't come out ...
9
votes
2answers
1k views

Expected performance of e-SATA port multiplication?

For a certain read/write workload, I get 30 MiB/s from a 4-disk array using esata port multiplication. When I move the exact same array to four individual sata connections, I get 90 MiB/s for the same ...
8
votes
9answers
14k views

How to find the number of open ports in linux?

How to find the number of open ports in linux? I want to see if I am running out of ports. Also, how do I see the limit of my OS?
8
votes
3answers
9k views

why can't macports find make

I am trying to run macports like thus: port install php5 When I do so, however, I get this error: Error: Unable to open port: can't read "build.cmd": Failed to locate 'make' in path: ...
8
votes
6answers
6k views

netstat shows a listening port with no pid but lsof does not

This question is similar to Network port open, but no process attached? I've tried everything from there, reviewed the logs, etc... and can't find anything. My netstat shows a TCP listening port and ...
8
votes
1answer
466 views

How do I specify port number for PuTTY to use with Windows cmd?

I start most of my SSH connections with a windows command like this cmd://"C:\Program Files\PuTTY\putty.exe" -ssh root@xxx.xx.xxx.xx I assume this defaults to port 22. Now I need to connect on a ...
7
votes
2answers
773 views

FreeBSD ports: remove build dependencies after installing port

Is there any way to remove build dependencies of the port after installing it? Many ports use exotic tools for building and these tools are not used anymore when port is builded and installed.
6
votes
3answers
2k views

Debian - Port 80 is blocked, but I don't know by what

I can't make lighttpd listen to port 80. ~# /etc/init.d/lighttpd start Starting web server: lighttpd2013-03-16 23:15:02: (network.c.379) can't bind to port: 80 Address already in use failed! ...
6
votes
4answers
2k views

What port should I open to allow remote desktop?

What port(s) should I open/NAT to allow me to use Remote Desktop?
6
votes
4answers
7k views

iphones and exchange, what am I missing?

I am trying to get iphones to play with our exchange 2010 server. I have opened ports 25 and 993 on the firewall, and I can get the account to validate, but I cannot send or receive email from it. ...
6
votes
3answers
344 views

What is the difference between these 2 iptables rules?

Trying to allow incoming ssh traffic on port 22. Default behavior is to DROP all incoming traffic. I came across 2 articles on how to allow traffic. However, they are different. ## open port ssh ...
6
votes
3answers
38k views

how to forward dns alias to hostname:port? [duplicate]

Possible Duplicate: How to use DNS to redirect domain to specific port on my server My web application is running on myserver.mydomain:10000 I would like to make it available on the ...
6
votes
6answers
15k views

How to check what port mysql is running on

On my windows dev box mysql is running on port 3306 How can I check what port it is running on the unix server that I have to upload the app to.
6
votes
1answer
10k views

Declaring multiple ports for the same VirtualHosts

Declare multiple ports for the same VirtualHosts: SSLStrictSNIVHostCheck off # Apache setup which will listen for and accept SSL connections on port 443. Listen 443 # Listen for virtual host requests ...
6
votes
1answer
208 views

Should I listen for SMTP on both 25 and 587?

I was setting up haraka as our mailing server, and for outbound email, it suggests moving to port 587 for SMTPS auth support. However, I'm unsure if I should be running 2 instances of haraka on ...
6
votes
2answers
3k views

Determine process using a port, without sudo

I'd like to find out which process (in particular, the process id) is using a given port. The one catch is, I don't want to use sudo, nor am I logged in as root. The processes I want this to work for ...
6
votes
3answers
4k views

How do I test the increased bandwidth after setting up LACP?

I have setup LACP, and LAG on our Netgear Switches (GS724T). I have bound(?) two ports together to create one 2Gbps connection between two of the switches. I was wondering if there is a way of ...
5
votes
6answers
819 views

How can I find the total number of TCP connections for a given port and period of time by IP?

On a Linux system there are plenty of methods for listing the current TCP connections for a given port by connecting IP but: how can I count the total number of connections to a port per source IP for ...
5
votes
5answers
3k views

Many ISP's is block port 25, how do I choose an alternative port?

I am building an application that will be acting as a combined MUA/MTA on different networks. However, many of the networks are with ISP's that block port 25 for SMTP. Therefore I would also like to ...
5
votes
2answers
234 views

Is there a way to tell a device name (computer name) which connects to the internet jack from a wall without accessing the switch to find out?

I'm not familiar with networking and have been trying to search for info online. From what I have found, there's no possible way to find out the particular physical port of a switch that a computer is ...
5
votes
4answers
2k views

How to make a URL point to a Tomcat instance?

Sorry if this question makes no sense (no expert here), but I understand that tomcat listens to port 8080 and that url are usually addressed to 80. Is there a way to tell DNS that urls should point to ...
5
votes
2answers
7k views

Node.js is not accessible from external IPs on Ubuntu

Hey everyone, I'm sure this is very noobish, so forgive me. I'm trying to run a node.js server on port 8080 of my ubuntu 10.04. Here's the result of iptables -L on the server: Chain INPUT (policy ...
5
votes
2answers
421 views

Where does a firewall application fit into the software stack?

I'm trying to figure out where a firewall application on a server fits into the software stack, and at what point in the networking process the firewall "kicks in," from the perspective of an ...
5
votes
1answer
782 views

Is it bad practice to run a web application server directly on port 80/443

I am hosting a web app on amazon aws, using an ec2 instance. On that instance i will be running only one application. using glassfish v3.0.1 I do not want to run the app using : ...
5
votes
1answer
4k views

How do I tell what is running on which ports in Ubuntu?

How could I tell what is listening on which ports on Ubuntu? In other words, how do I get a list of ports that are in use? Thanks, Alex
5
votes
8answers
6k views

Used/blocked ports in Ubuntu

starting up Glassfish AS would tell me the port 4848 is blocked (or any port that I configure). But checking the ports are not used. There is no firewall. root@ubuntu:~/glassfishv3/glassfish/bin# ...
5
votes
1answer
3k views

Selecting Interface for SSH Port Forwarding

I have a server that we'll call hub-server.tld with three IP addresses 100.200.130.121, 100.200.130.122, and 100.200.130.123. I have three different machines that are behind a firewall, but I want to ...
5
votes
8answers
3k views

Looking for a small, portable, port-mirroring ethernet switch

I recently had a mac go haywire, taking half a minute or more to get www.google.com loaded. Getting its owner to give up the machine for repair was like pulling teeth - they were insisting that it ...