I got everything major working like GET, PUT and POST with multipart/form-data and reading chunked encoding and all that stuff. Not too hard since there are open source http libraries for every major language. I looked at ruby Net::HTTP (stole some regex’s) and Apache Httpclient (stole your multipart boundary).

I got to the point where I was testing uploading larger files, like in:

var client:HttpClient = new HttpClient();
var uri:URI = new URI("http://mybucket.s3.amazonaws.com/big.mp3");
var testFile:File = new File("app:/test/assets/big.mp3");
client.upload(uri, testFile);

It turns out that when you call _socket.flush() (in HttpSocket) it doesn’t actually block, which you might expect. After thinking on it, this isn’t totally shocking since the whole threading model behind actionscript, you don’t really ever block (like there is no such thing as a modal dialog in flash). The problem is without blocking or an event to notify of a flush, the socket just gets filled with the request body all at once (all 800MB’s or whatever file size).

It turns out other people ran into this as well. If you look at (FlexFTP) source, the UploadInv.as file, you will see block of code commented out and replaced by a setInterval(.. , 300). Nice. I guess that upload is capped at ~12kb/sec.

Any of the links in the comments off this blog post are useful too.

If you look at FileStream object you will see it has an outputProgressEvent so that would be useful, you know, if Socket had that too.

I don’t know how you get around this issue, other than trying to guess how fast the socket can transmit and try to stay under that. So now I’m not sure what to do, other than abandon it and come back to it when its fixed, which hopefully will be soon. Thankfully, I can go back to ruby and maybe play with some RubyCocoa or Shoes framework.

Update: Feel free to chime in at Adobe Air Forum or Feature Request/Bug Report Form