Port in Use When Not Using a Port

How do I kill the process currently using a port on localhost in Windows?

Step 1:

Open up cmd.exe (note: you may need to run it as an administrator, but this isn't always necessary), then run the below command:

netstat -ano | findstr :<PORT>

(Replace <PORT> with the port number you want, but keep the colon)

The area circled in red shows the PID (process identifier). Locate the PID of the process that's using the port you want.

Step 2:

Next, run the following command:

taskkill /PID <PID> /F

(No colon this time)

Lastly, you can check whether the operation succeeded or not by re-running the command in "Step 1". If it was successful you shouldn't see any more search results for that port number.

What port number shall I use?

ports within 0 to 1023 are generally controlled and you should assign your socket with higher port numbers, although in that range ports within 1024 and 49151 can be registered for others to be informed about that and not use them.

if you want to avoid conflicts you can see registered ports on your machine and assign a port number to your socket which is empty but ports higher than that (49152 to 65535) are completely free and are not even registered.

generally, it is not common to worry about that. for example, two major applications like VMware and apache web server operate on the same port number (443), and if you want to use VMware workstation and Xampp (which works with apache) you have to simply make one of them listen on another port and its not a big deal. so in my opinion the best practice is to let your users change this via a config file or something similar.

for further information, you can search google. for instance this link might be useful:

https://www.sciencedirect.com/topics/computer-science/registered-port#:~:text=Well%2Dknown%20ports%E2%80%94Ports%20in,1023%20are%20assigned%20and%20controlled.&text=Registered%20ports%E2%80%94Ports%20in%20the,be%20registered%20to%20prevent%20duplication.&text=Dynamic%20ports%E2%80%94Ports%20in%20the,assigned%2C%20controlled%2C%20or%20registered.

How to make sure that a certain Port is not occupied by any other process

You can use "netstat" to check whether a port is available or not.

Use the netstat -anp | find "port number" command to find whether a port is occupied by an another process or not. If it is occupied by an another process, it will show the process id of that process.

You have to put : before port number to get the actual output

Ex
netstat -anp | find ":8080"

Tomcat Server Error - Port 8080 already in use

All I had to do was to change the port numbers.

1. Open Eclipse

2. Go to Servers panel

3. Right click on Tomcat Server select Open, Overview window will appear.

4. Open the Portstab. You will get the following:

   • Tomcat adminport

   • HTTP/1.1

   • AJP/1.3

5. I changed the port number of HTTP/1.1 (i.e. to 8081)

6. You might have to also change the port of Tomcat adminport (i.e. to 8006) and of AJP/1.3 (i.e. to 8010).

7. Access your app in the browser at http://localhost:8081/...

How do I find out which process is listening on a TCP or UDP port on Windows?

PowerShell

TCP

Get-Process -Id (Get-NetTCPConnection -LocalPort YourPortNumberHere).OwningProcess

UDP

Get-Process -Id (Get-NetUDPEndpoint -LocalPort YourPortNumberHere).OwningProcess

cmd

 netstat -a -b

(Add -n to stop it trying to resolve hostnames, which will make it a lot faster.)

Note Dane's recommendation for TCPView. It looks very useful!

-a Displays all connections and listening ports.

-b Displays the executable involved in creating each connection or listening port. In some cases well-known executables host multiple independent components, and in these cases the sequence of components involved in creating the connection or listening port is displayed. In this case the executable name is in [] at the bottom, on top is the component it called, and so forth until TCP/IP was reached. Note that this option can be time-consuming and will fail unless you have sufficient permissions.

-n Displays addresses and port numbers in numerical form.

-o Displays the owning process ID associated with each connection.

Why and how to fix? IIS Express The specified port is in use

i solve the problem this way...

File -> Open -> Web Site...

After that select Local IIS under IIS Express Site
remove the unwanted project.

hope this help.

How do I determine if a port is open on a Windows server?

Assuming that it's a TCP (rather than UDP) port that you're trying to use:

1. On the server itself, use netstat -an to check to see which ports are listening.

2. From outside, just use telnet host port (or telnet host:port on Unix systems) to see if the connection is refused, accepted, or timeouts.

On that latter test, then in general:

• connection refused means that nothing is running on that port
• accepted means that something is running on that port
• timeout means that a firewall is blocking access

On Windows 7 or Windows Vista the default option 'telnet' is not recognized as an internal or external command, operable program or batch file. To solve this, just enable it: Click *Start** → Control Panel → Programs → Turn Windows Features on or off. In the list, scroll down and select Telnet Client and click OK.

Web server failed to start. Port 8080 was already in use. Spring Boot microservice

If you don't want the embedded server to start, just set the following property in you application.properties (or .yml):

spring.main.web-application-type=none

If your classpath contains the necessary bits to start a web server, Spring Boot will automatically start it. To disable this behaviour configure the WebApplicationType in your application.properties

Source: https://docs.spring.io/spring-boot/docs/current/reference/html/howto-embedded-web-servers.html

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If you application really is a Web application, then you can easily change the port using the server.port property (in your application's .properties/.yaml file, as a command line argument at startup, etc).

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