HTTP headers for chunked encoding POST - Error 411

Question

I'm sending data to a server with an Arduino which requires constructing an HTML POST line-by-line. I don't necessarily know the Content-Length a-priori, so I am using "chunked" encoding.

When I tried this example post from Wikipedia with the "Transfer-Encoding" option as specified in rfc2616

client.println("POST /myurl HTTP/1.1");
client.println("Host: 12.345.679.999"); // replaced with the test server's IP
client.println("User-Agent: Arduino/1.0");
client.println("Transfer-Encoding: chunked");
client.println();  
client.println("4");
client.println("test");
client.println("0");
client.println();

or, with escape characters explicit:

client.print("4\r\ntest\r\n0\r\n\r\n");

I receive the error from my server:

HTTP/1.1 411 Length Required
A request of the requested method POST requires a valid Content-length.
Server: Apache/2.2.22 (Ubuntu)

However, "chunked" encoding shouldn't require a Content-Length header field, see 4.4 - Message Length in rfc2616

Am I missing a field? Why doesn't this call work?

For the record, the non-Chunked-Encoding works:

if(client.connect(server, 80)){
    String PostData = "test";
    Serial.println("POST /myurl HTTP/1.1");
    client.println("Host: 12.345.679.999"); // replaced with the test server's IP
    Serial.println("User-Agent: Arduino/1.0");
    Serial.print("Content-Length: ");
    Serial.println(PostData.length());
    Serial.println();
    Serial.println(PostData);
}

UPDATE

From the apache2 error.log: "chunked Transfer-Encoding forbidden"

Answer 1

After finding

chunked Transfer-Encoding forbidden

in my Apache2 log I concluded that the error was not in the POST that I was making.

I found that modwsgi (the middle-layer between apache and django) does not enable chunked transfer-encoding by default. In the past, chunked wasn't supported at all

Refering to the change-log in the new version of modwsgi, I found that writing

WSGIChunkedRequest On

in my apache httpd.conf file allowed chunked requests (no more 411 error)