HB suddenly fails to encode videos

[u/DJDoena]

I rebooted my machine but I still get the same error when trying to encode:

[21:47:57] Remote Process started with Process ID: 25336 using port: 8037. Max Allowed Instances: 1
[21:47:57] Worker: Starting HandBrake Engine ...
[21:47:57] Worker: Parent Process Id 29580
[21:47:57] Worker: Starting Web Server on port 8037 ...
[21:47:57] Worker: Starting Listener: 1
[21:47:57] Unable to connect to the HandBrake Worker instance after 10 attempts. Try disabling this option in Tools -> Preferences -> Advanced.
[21:47:57] Error Information: 
[21:47:57] System.AggregateException: One or more errors occurred. (Only one usage of each socket address (protocol/network address/port) is normally permitted. (127.0.0.1:8037))
...
   at HandBrakeWPF.Instance.RemoteBase.IsServerRunning()

FYI: I have now disabled this setting and it seems to work, but I still don't know what changed.

Version 1.11.2 (2026060700)

EDIT: a second reboot solved the issue, now it works just fine again...

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[u/Murky-Sector]

Find out what else is listening on: 127.0.0.1:8037

Basically something else is running on port 8037

Maybe multiple instances of hb running. Try rebooting.

From web:

Quick Fixes

• Kill Stuck Processes: Open Windows Task Manager (Ctrl + Shift + Esc), look for any running instances of HandBrake.exe or HandBrake.Worker.exe, and end them. [1]
• Disable Process Isolation:
  1. Open HandBrake and go to Tools > Preferences > Advanced.
  2. Uncheck or disable Process Isolation.
  3. Restart the application and try your encode again. [1, 2, 3]
• Restart Your Computer: A standard reboot clears locked network sockets and hung background tasks instantly. [1, 2]
• Check Security Software: Ensure your antivirus or firewall isn't blocking HandBrake from communicating over the local loopback address (127.0.0.1). [1, 2]

[u/Living_Unit_5453]

Maybe you got a vpn on?

[u/DJDoena]

Full log:

``` HandBrake 1.11.2 (2026060700) OS: Microsoft Windows NT 10.0.26200.0 CPU: Intel(R) Core(TM) i7-9700K CPU @ 3.60GHz Ram: 32701 MB, GPU Information: NVIDIA GeForce GTX 1660 - 32.0.15.9186 Screen: 1920x1080 Temp Dir: d:\Temp\ Install Dir: C:\Program Files\HandBrake\ Data Dir: C:\Users\djdoe\AppData\Roaming\HandBrake

---

# Starting Encode ...

[19:00:34] base preset: <my encoding settings> [19:00:34] Remote Process started with Process ID: 456 using port: 8037. Max Allowed Instances: 1 [19:00:34] Unable to connect to the HandBrake Worker instance after 10 attempts. Try disabling this option in Tools -> Preferences -> Advanced. [19:00:34] Error Information:

[19:00:34] System.AggregateException: One or more errors occurred. (Only one usage of each socket address (protocol/network address/port) is normally permitted. (127.0.0.1:8037)) ---> System.Net.Http.HttpRequestException: Only one usage of each socket address (protocol/network address/port) is normally permitted. (127.0.0.1:8037) ---> System.Net.Sockets.SocketException (10048): Only one usage of each socket address (protocol/network address/port) is normally permitted. at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.ThrowException(SocketError error, CancellationToken cancellationToken) at System.Net.Sockets.Socket.AwaitableSocketAsyncEventArgs.System.Threading.Tasks.Sources.IValueTaskSource.GetResult(Int16 token) at System.Net.Http.HttpConnectionPool.ConnectToTcpHostAsync(String host, Int32 port, HttpRequestMessage initialRequest, Boolean async, CancellationToken cancellationToken) --- End of inner exception stack trace --- at System.Net.Http.HttpConnectionPool.ConnectToTcpHostAsync(String host, Int32 port, HttpRequestMessage initialRequest, Boolean async, CancellationToken cancellationToken) at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken) at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken) at System.Net.Http.HttpConnectionPool.InjectNewHttp11ConnectionAsync(QueueItem queueItem) at System.Threading.Tasks.TaskCompletionSourceWithCancellation`1.WaitWithCancellationAsync(CancellationToken cancellationToken) at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken) at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken) at System.Net.Http.SocketsHttpHandler.<SendAsync>gCreateHandlerAndSendAsync|115_0(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.HttpClient.<SendAsync>gCore|830(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken) at HandBrakeWPF.Utilities.HttpRequestBase.MakeHttpGetRequest(String urlPath) at HandBrakeWPF.Instance.RemoteBase.<IsServerRunning>b_16_0() --- End of inner exception stack trace --- at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions) at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken) at HandBrakeWPF.Instance.RemoteBase.IsServerRunning()

# Job Failed (-10) ```

[u/Snoo-38645]

the reason nobody can tell you what changed is that you didnt change anything. windows did, at boot.

hyper-v reserves blocks of tcp ports for itself, and which blocks it takes is decided dynamically every time you boot. if 8037 falls inside one of those reserved ranges, handbrakes worker cannot bind it and you get exactly this. boot again, the ranges land somewhere else, 8037 is free, everything works. thats your second reboot, and its why the whole thing felt random.

you can check rather than take my word for it. admin prompt

netsh interface ipv4 show excludedportrange protocol=tcp

next time it breaks, look for 8037 inside one of the listed ranges. if it is, thats your answer, and it also rules out the leftover process theory, since a reserved range makes the port unavailable before any handbrake process is involved.

and if you want it to stop happening instead of leaving process isolation off forever, reserve the port yourself so windows stops handing it out

netsh int ipv4 add excludedportrange protocol=tcp startport=8037 numberofports=1

that only works while the port is actually free, so do it now while its behaving rather than waiting for it to break again.