The issue:
$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
[default] Setting the name of the VM...
[default] Clearing any previously set forwarded ports...
[default] Fixed port collision for 22 => 2222. Now on port 2200.
Vagrant cannot forward the specified ports on this VM, since they
would collide with some other application that is already listening
on these ports. The forwarded port to 4000 is already in use
on the host machine.
To fix this, modify your current projects Vagrantfile to use another
port. Example, where '1234' would be replaced by a unique host port:
config.vm.network :forwarded_port, guest: 4000, host: 1234
Sometimes, Vagrant will attempt to auto-correct this for you. In this
case, Vagrant was unable to. This is usually because the guest machine
is in a state which doesn't allow modifying port forwarding.
Find out what processes are listening (and on what port).
$ lsof -i | grep LISTEN
GoogleTal 537 jhelms 29u IPv4 0xffffff801ac71fa0 0t0 TCP localhost:49231 (LISTEN)
GoogleTal 537 jhelms 33u IPv4 0xffffff801b2c6a40 0t0 TCP localhost:49232 (LISTEN)
Adium 565 jhelms 8u IPv4 0xffffff8014cd44e0 0t0 TCP *:5298 (LISTEN)
Adium 565 jhelms 9u IPv4 0xffffff8014cd44e0 0t0 TCP *:5298 (LISTEN)
VBoxHeadl 1503 jhelms 29u IPv4 0xffffff802577bfa0 0t0 TCP localhost:rockwell-csp2 (LISTEN)
VBoxHeadl 1503 jhelms 30u IPv4 0xffffff8026296c20 0t0 TCP *:terabase (LISTEN)
If there is a process listed on port 4000, kill it. If there are any headless processes, kill those as well.
$ kill <pid>
The in the above example would be 1503 as that process is in a headless state.
If you're missing the command you should install the binary for it and try again. If you're on Windows maybe try
netstat -binstead? Not sure what else to say, the gist is accurate. 🤷♂️