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I found a similar question (Error: incorrect header check at Zlib._handle.onerror (zlib.js:355:17) errno: -3, code: 'Z_DATA_ERROR') but that has not been answered. I have not seen anything on Google forums either.

background:

• I ported zlib into my project


• I do not have a file system, so compress() is fed a report constructed as a JSON string.


• I know the JSON string is acceptable because if I POST it without compression everything works.


• I am using zlib in its simplest form (see Using zlib deflateBound() dynamically)


• If I do a self check (i.e. instead of sending the compressed message to the server, I feed it into deflate then compare the output to the original) everything look fine.

Symptoms

• The response I get to the POST is "status":400,"error":"incorrect header check"


• 
  

  The server team is telling me that the error is thrown by gunzip so I am assuming the problem is with the gzip header, not the HTTP header.

  
  
  

  message: " Error: incorrect header check
  at Gunzip.zlibOnError (zlib.js:153:15)
  errno: -3,
  code: 'Z_DATA_ERROR',
  expose: true,
  statusCode: 400,
  status: 400 "

  
  

Is there some magic setting in either end that is needed for this? I have not found a Google document that says "use these settings for compression (not that zlib has a lot of settings)

Edit: everything I see mentions compressing files. In fact the few samples I saw all show a filename if you look in the gzip header. In my case, there is no file or filename, compress works on a string in memory and we send the resulting binary array directly. I am nto sure if this makes a difference.

I found the problem: "Content-Encoding" was set to "gzip" but since I am sending a zlibstream rather than a .gz file, it should have been set to "deflate".

See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Encoding for details.