How to implement Video Seek support with an embedd

I have a client iOS application that uses GCDWebServer to serve images and videos stored in the NSSearchPathDirectory.DocumentDirectory folder of the app on my device.

Upon app startup, I start an instance of GCDWebServer and add a file response handler for my requests:

self.addDefaultHandlerForMethod("GET", requestClass: GCDWebServerFileRequest.self) { request in

    return GCDWebServerFileResponse(file: self.filePathForResponse(request.URL))
}

I can verify that while the app is running I can successfully download files from my device:

curl -O http://192.168.0.15:8080/files/IMG_1213-1280x720.MOV

My app talks to a Chromecast device by sending URLs like the one above to a media channel, and the Chromecast receiver app loads and plays the videos at the specified URLs - so far all good.

My problem is that I want to implement seeking support for the currently playing video, and as soon as I send a seek request to the media channel, I get a "Broken pipe" error from GCDWebServer and the video playback is interrupted. Log from the server is as follows:

....
[DEBUG] Connection sent 32768 bytes on socket 24
[DEBUG] Connection sent 32768 bytes on socket 24
[ERROR] Error while writing to socket 24: Broken pipe (32)
[DEBUG] Did close connection on socket 24

My best understanding of the problem is that normal playback works because it is the same as downloading a file from beginning to end and this can be served with a regular GCDWebServerFileResponse, however seeking is equivalent to 'jumping' to a different part of the file and I'm not sure that reading a file like this would work with my configuration.

Is there a way that I can configure GCDWebServer to make this work? I know that the problem can be solved because there are several live apps that do this.
Do I need to use a server that supports other protocols such as HLS or RTSP?
Do I need to encode my video files in a particular manner?

For reference I have also tried another HTTP server called Swifter but I encountered the same problem.

iOS' AVPlayer at first requests file size and then asks server for a chunks of data, including a desired range in the request. In this answer, the network activity of AVPlayer is shown, and the response status code is 206, i.e. Partial Content.

So, we need to respond only with desired chunk of data:

webServer?.addDefaultHandlerForMethod("GET", requestClass: GCDWebServerRequest.self, asyncProcessBlock: { (request, completionBlock) in
  let response = GCDWebServerFileResponse(file: path, byteRange: request.byteRange)
  completionBlock(response)
})

Please, notice, that it is important to check, whether request.byteRange is defined by invoking request.hasByteRange().

Using the code I've provided, I was able to play a video using AVPlayer or web browser and scrubbing / seek to time worked perfectly.