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.

learn more… | top users | synonyms

60
votes
3answers
417k views

How to check if a port is blocked on a Windows machine?

On the Windows platform, what native options to I have to check if a port (3306, for example) on my local machine (as in localhost), is being blocked?
54
votes
6answers
261k views

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

How can I check if a port is listening on a Linux server?
51
votes
4answers
51k 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?
50
votes
11answers
10k 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 ...
38
votes
16answers
37k 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 ...
35
votes
4answers
19k 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 ...
31
votes
1answer
53k 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 ...
28
votes
8answers
20k 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 ...
27
votes
5answers
70k 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 ...
26
votes
2answers
42k 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?
25
votes
8answers
90k views

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

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.
24
votes
9answers
63k 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?
22
votes
7answers
148k 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 ...
18
votes
1answer
9k views

Why MySQL command line tool ignores --port parameter?

This is what I'm doing: mysql --host=localhost --port=9999 mysql -u root -p --execute="show tables;" The command works (connecting to port 3306) no matter what I provide in --port argument. I have ...
18
votes
11answers
221k 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 ...
18
votes
1answer
22k 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 ...
17
votes
9answers
124k 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 ...
17
votes
4answers
8k 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 ...
17
votes
1answer
12k 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 ...
16
votes
5answers
10k 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 ...
16
votes
4answers
42k 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 ...
15
votes
1answer
10k views

nginx: no permission to bind port 8090 but it binds to 80 and 8080

I'm struggling with some strange permission related behavior: when I configure nginx to listen to port 8080 everything works as expected, but when I use any other port I get something like 2014/01/10 ...
13
votes
3answers
46k views

Opening up port 8080 in CentOS

I'm new to opening up ports in CentOS. I need to open up tcp port 8080 and have installed/ran nmap to find it is not open already. I've been reading about the iptables command, I have v1.3.5 installed ...
13
votes
8answers
42k 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 ...
13
votes
2answers
1k 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 ...
12
votes
6answers
50k 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.
11
votes
5answers
14k 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 ...
11
votes
4answers
14k 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
9answers
26k 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?
10
votes
2answers
10k views

Nmap not scanning all ports

I've noticed that nmap only scans a bunch of known ports, and the only way i've managed to check 'em all is to put a "-p 0-65535" in. Why is that? am I wrong? is there a more popular way to scan all ...
10
votes
3answers
79k 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 ...
10
votes
1answer
11k 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 ...
10
votes
1answer
10k 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
10
votes
2answers
2k 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 ...
10
votes
1answer
16k views

Failed to connect to 127.0.0.1 port 80

I have running nginx server (doesn't matter which server): $ sudo netstat -tulpn | grep 80 tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 4268/nginx tcp6 0 0 :::80 ...
9
votes
3answers
319 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
6answers
21k views

Windows Server 2008 without telnet client - how to test connecting to remote ports without installing anything new?

I'm looking to see if anyone knows of slick tricks to test connections to remote server ports from Windows server 2008 and variants that don't include the telnet client installed by default. Reason ...
8
votes
3answers
4k 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! ...
8
votes
4answers
24k views

Monitor ssh on non-default port with Nagios

I just deployed Nagios on a Gentoo server and everything is fine except ssh, which it marks as "CRITICAL" because it's refusing connections. But that's because it's running on a port different from ...
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
1answer
570 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 ...
8
votes
1answer
2k views

mosh-like port forwarding

This is on linux, connecting to linux servers: I love mosh, but it doesn't support port forwarding, and likely won't for a while since it's been almost a year now and it hasn't happened yet. port ...
7
votes
2answers
20k views

check port open without telnet [closed]

What do people use when Telnet is not installed to check a port is open and reachable? E.g. I used to use the technique of telnet <destination> and know it was there, even if telnet could not ...
7
votes
4answers
10k 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. ...
7
votes
4answers
5k 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 ...
7
votes
7answers
51k views

FTP hangs on: 150 Opening ASCII mode data connection

I am setting up an FTP server on my Windows 2008 server (R2). Everything appears to be installed correctly but I am having trouble using an FTP Client to login to my FTP server. I can remote desktop ...
7
votes
1answer
9k views

On Linux, how can I tell how many ephemeral ports are left available?

Is there a method in Linux to check how many ephemeral ports are left available? I occasionally see "Address already in use" errors as a result of running out of ephemeral ports. A machine reboot will ...
6
votes
5answers
34k 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
3answers
12k views

How to assign a hostname to SSH tunnel

I'm using ssh root@my.server.ip -g -L 4321:localhost:28017 to establish a tunnel from my MacBook to my dedicated server at my hosting provider. It works well. Now I want to access several admin sites ...
6
votes
3answers
503 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 ...