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How to find which port a server uses for coding bootcamp students

Learn how coding bootcamp students find which port a local dev server uses, and how to fix port conflicts when they happen.

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Check the start command, the project's config files, or the address printed when the server starts. If a port is already taken, a list of running processes shows which program holds it.

OptionWhat it doesCost
DevWebUIStarts, stops and restarts local dev servers from one dashboard, and shows each one's status, CPU, memory and logs. [1]Free, and core features need no account. [1]
Terminal commandsPlain commands you type to start, stop and check each server yourself.not published
Editor run settingsSaved run settings inside a code editor that start project commands.not published

What you need before you start

Before you can find a server's port, you need the project open on your own computer and the command that starts the server at hand. Most projects set the port in one of a few places: the start script in the project's package file, an environment file, or the framework's config file. Some servers also print the address they opened when they start, so keep that startup output visible.

Write down which server you are looking for, such as a frontend, an API, or a database, because each one can use its own port. Make sure the project's packages are installed and that the server actually starts before you search. A server that failed to start will not be holding a port.

Know which operating system you use. The commands for listing ports differ on Windows and on macOS or Linux. A notes file with the project name and each port you find will save time when you come back to the project later.

Step by step

  1. Open the project folder and find the command that starts the server. Look in the project's package file for the script that runs it.
  1. Search the config files for a port setting. Check environment files and framework config files for the word port.
  1. Read the startup output. Many servers print the address they listen on when they start, so the port often appears there.
  1. Test the address. Open the address in a browser to confirm the server responds on that port.
  1. If no port appears, list the ports in use. On macOS or Linux, run lsof -iTCP -sTCP:LISTEN -P -n in the terminal. On Windows, run netstat -ano | findstr LISTENING in a command prompt.
  1. Match the process to your server. Compare the process name or ID in that list with the server you started, so you know which entry belongs to it.
  1. Record the port. Write it down beside the server's name so the next search is shorter.
  1. Confirm by restarting. Stop the server, start it again, and check that the same port comes back. That shows the match is right.

Tools that can do it

DevWebUI is made by the team that publishes this site, SayDeploy. It lets you start, stop and restart local dev servers from one dashboard, and see each one's status, CPU, memory and logs. [1] When a port is already taken, it shows which process holds that port and can free the port if you ask. [1] Errors from your servers are collected into one log, and each file and line link opens in your editor. [1]

DevWebUI can also use one small file per repo to list the servers to run, and it writes changes made in the dashboard back to that file. [1] On Windows, download devwebui-windows-x64.exe from GitHub Releases. [1] On any system, you can run bun install and then bun run dev. [1] On systems other than Windows, you run it from source with Bun, a JavaScript runtime, and the tray app is Windows-only for now. [1]

Other options are plain terminal commands, saved scripts, and the run settings built into many code editors. Check each option's own documentation for how it reports ports, logs and startup order before you choose one. The right pick depends on how many servers your project runs and how comfortable you are with the command line.

Common mistakes to avoid

Starting several servers without writing down their ports makes conflicts hard to trace. Two servers set to the same port will compete for it, and the second one often fails to start with an error that is easy to miss.

Reading only the last line of output can hide the port, so scroll up to the startup messages. Searching for a port that no server is using wastes time, so confirm the server is running first. Changing a port in one file but not in the front end that calls it can break the connection between them.

Closing a terminal window does not always stop the server behind it, which can leave an old process holding its port. Check for leftover processes before starting again. Keeping a short note of each port costs very little and saves a search the next time.

Frequently asked questions

How can coding bootcamp students find which port a dev server uses?

They can check the project's start command and config files, read the address printed when the server starts, or list the processes that are listening on the computer. Once a port is found, test it in a browser to confirm the server responds there. Writing the port down beside the server's name makes the next search faster. The steps above cover each of these checks in order, so the same method works for most projects.

What should students do when a port is already taken?

First identify which process holds the port, using the commands in the steps above or a tool that lists it. Then decide whether that process is an old copy of the server that can safely be stopped, or another project that needs its own port. If it is safe to stop, stop it and start the server again. If not, change the port in that project's settings and restart it.

Does DevWebUI show which process holds a port?

Yes. When a port is already taken, DevWebUI shows which process holds it and can free the port if asked. [1] It also shows the status of each local dev server it manages, so the server you started can be checked from the same dashboard. [1] Students who are unsure which server is which can check the dashboard before stopping anything.

Is DevWebUI free for coding bootcamp students?

DevWebUI is free, and its core features need no account. [1] It is open source under the MIT License. [1] On Windows, the prebuilt app can be downloaded from GitHub Releases. [1] On other systems, it runs from source with Bun. [1] Check the project's own pages for the current details before you install it.

Can DevWebUI collect errors from several dev servers into one place?

DevWebUI collects errors into one log that merges repeats and is kept across restarts. [1] Each file and line link opens in your editor, so you can go straight from a message to the code it points at. Keeping the log across restarts means errors from an earlier run remain available to review after you start the servers again.

DevWebUI is free, and its core features need no account. [1]

Try DevWebUI

Sources

  1. DevWebUI's own description of itself (the product of this site's publisher)

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