http-content-length

I'm currently trying to optimize http-based data transfer between several applications. Our current approach, downloading first and then creating the post-request, obviously add extra IO/memory load and latencies, which I'd like to circumvent. The core question of all: Is it required to send a "Content-Length" header in HTTP POST requests? IIRC, HTTP 2616 declares that it's optional, but I'm not sure how applications actually behave at this point. Depends what you mean by optional. If you mean that you can just omit the header anytime you like then no, it is not optional. The HTTP spec has

I'm using the python requests module to do some testing against a site. The requests module allows you to remove certain headers by passing in a dictionary with the keys set to None. For example headers = {u'User-Agent': None} will ensure that no user agent is sent with the request. However, it seems that when I post data, requests will calculate the correct Content-Length for me even if I specify None, or an incorrect value. Eg. headers = {u'Content-Length': u'999'} headers = {u'Content-Length': None} I check the response for the headers used in the request (response.request.headers) and I