Django: That port is already in use. What to do about port 8000
Django fails loudly instead of moving, which is the better behaviour. Finding the leftover runserver, the autoreloader's second process, and the Docker case.
September 14, 2026
Blog
RSSPractical fixes for the network problems Bosun exists to solve.
Troubleshooting14
Express EADDRINUSE: the framework gives you nothing, so handle it yourself
Express does not catch this for you. The fix, why nodemon makes it worse, and the few lines that turn a stack trace into a useful message.
September 14, 2026
MySQL port 3306 already in use: Homebrew, MAMP, Docker, and the socket confusion
3306 conflicts are almost always a second MySQL you forgot about. Which manager owns it, and why the socket error is a different problem entirely.
September 14, 2026
Next.js port 3000 in use: pinning the port and finding the leftover server
Next.js moves to 3001 rather than failing, which quietly breaks anything expecting a fixed URL. How to pin the port and clear whatever took 3000.
September 14, 2026
PostgreSQL port 5432 already in use: the one where killing the process does not help
Postgres is usually started by a service manager, so killing the PID just brings it back. Homebrew, Docker and stale postmaster.pid files, and what each one needs.
September 14, 2026
Rails says a server is already running: the pid file, and the port
Rails has its own version of this error that has nothing to do with the port being busy. Telling the two apart is the whole fix.
September 14, 2026
React: Something is already running on port 3000. Would you like to run on another port?
Create React App asks instead of failing or moving. Saying yes is usually the wrong answer, and here is what to do instead.
September 14, 2026
Redis 6379 already in use: check whether you even need to start one
Could not create server TCP listening socket *:6379. Before killing anything, one command tells you whether a working Redis is already there.
September 14, 2026
Vite port 5173 already in use: why it usually moves, and what to do when it should not
Vite quietly picks the next free port instead of failing, which is helpful until it is not. How strictPort works and how to find what took 5173.
September 14, 2026
Kill all the stuck Node processes on your Mac (without nuking your editor)
Orphaned node dev servers eating RAM and holding ports on macOS? See every Node process and kill the stuck ones, without taking out your editor's language servers.
July 20, 2026
Docker Desktop eating CPU on your Mac? How to find (and kill) the culprit
Fan spinning and Mac sluggish because of Docker Desktop? Find out if it's Docker overall or one container, and what actually fixes the CPU spike.
July 15, 2026
Docker: "bind: address already in use" on Mac (lsof won't tell you which container)
Docker port conflicts on Mac don't show up in lsof the way you'd expect. Find the real container with docker ps, stop it the right way, and stop guessing.
July 15, 2026
ngrok says tunnel already running (ERR_NGROK_108 / ERR_NGROK_334)? Here's the fix
Fix ngrok's ERR_NGROK_108 and ERR_NGROK_334 tunnel-already-running errors on Mac: find the orphaned process, kill it, and check what's actually tunneling.
July 15, 2026
Port 3000 already in use on your Mac? Here's how to actually fix it
Fix EADDRINUSE and "port already in use" errors on macOS: find the process with lsof, kill it the right way, and stop it from happening again.
July 15, 2026
Basics5
Port number ranges explained: which ports you can use and which you should not
The 65,536 ports are split into three ranges with different rules. Knowing where yours sits explains permission errors and mysterious conflicts.
September 14, 2026
TCP vs UDP, explained through the ports on your own machine
The difference matters more than most tutorials suggest, especially when a port looks free in one tool and busy in another. A practical look, not a textbook one.
September 14, 2026
What is a port, actually? A practical explanation for developers
Ports are not physical, there are exactly 65,536 of them, and only one process can listen on each. Here is what that means day to day on a Mac.
September 14, 2026
What is EADDRINUSE? The error, the cause, and the case where nothing is listening
EADDRINUSE is an operating system error code, not a Node one. Here is what it means, why it happens, and the TIME_WAIT case where lsof shows nothing at all.
September 14, 2026
What is localhost? 127.0.0.1, ::1 and why your dev server lives there
localhost is a name that points at your own machine and never touches the network. Here is what that means for dev servers, Docker and why 0.0.0.0 is different.
September 14, 2026
Comparisons3
Bosun vs Activity Monitor: why the built in tool cannot answer port questions
Activity Monitor is already on your Mac and it is genuinely good at what it does. Ports are simply not one of those things, and here is why.
September 14, 2026
Bosun vs the free port apps: a fair comparison
There are several good free menu bar port tools for macOS, some of them excellent. Here is what each one does well and where Bosun is actually different.
September 14, 2026
Bosun vs lsof: when is a menu bar app worth it over a one liner?
An honest comparison. lsof is free, already installed, and handles most port problems in one command. Here is exactly where it stops being enough.
September 14, 2026