Rust HTTP server on Heroku generates error H18 — Server Request Interrupted - heroku

Question

The Problem
I am trying to host a simple HTTP server written in Rust on Heroku.
I am not using an external HTTP library because this is a learning project for University, so I am managing everything through TcpStreams.
The server works as expected locally.
I keep seeing the H18 (Server Request Interrupted) error in the Heroku logs, and the running instance on Heroku does not serve any files. Specifically, these types of errors occur:
2017-03-12T14:11:53.952084+00:00 heroku[router]: sock=backend at=error code=H18 desc="Server Request Interrupted" method=GET path="/" host=regans-rust-project.herokuapp.com request_id=fe50b113-8091-4129-99f5-632c9536bb8e fwd="154.126.208.8" dyno=web.1 connect=0ms service=2ms status=503 bytes=581 protocol=https
2017-03-12T14:11:54.459277+00:00 heroku[router]: sock=backend at=error code=H18 desc="Server Request Interrupted" method=GET path="/favicon.ico" host=regans-rust-project.herokuapp.com request_id=cf6ad8a0-2780-4c07-843a-2b533df1c9aa fwd="154.126.208.8" dyno=web.1 connect=0ms service=1ms status=503 bytes=388 protocol=https
What I have tried
I have made sure that the static resources are in the directory by invoking Heroku's bash utility. I have also run the executable from here, and the server works locally from the Heroku instance as well.
I have ensured that I am returning well-formed HTTP responses (I have status codes, content types, connection types, content lengths).
My Code
You can see my code here.
I am using the following buildpack
Is there anything else I should be appending to my responses to "finish" them? Any help would be greatly appreciated :)

Answer 1

As discussed in the comments, the problem was that the code was using \n as the delimiter in the HTTP response whereas the standard says it should be \r\n

Answer 2

I also faced this error testing a POST call to process the image file at Flask server.
I added a simple delay before returning the response
time.sleep(3)
It worked!
I believe Heroku(a free subscription) needs time to process the POST request from infrastructure angle, so it was throwing the network error if you return immediately
Before
#app.route("/process_image", methods=['POST'])
def process_image():
print ("received ")
return json.dumps({'success': True}), 200, {'ContentType': 'application/json'}
Later
#app.route("/process_image", methods=['POST'])
def process_image():
print ("received ")
time.sleep(3)
return json.dumps({'success': True}), 200, {'ContentType': 'application/json'}