HTTP 1xx Status Codes

Question

Does anyone of you has ever seen a real life occurence of the HTTP "Expect" header? Or any proxy or server answering with a "100 Continue"-Status Message? Do popular HTTP servers like IIS or Apache ever encounter situations where a "100 Continue" is returned?

Thanks, Max

Answer 1

libcurl will add the "Expect: 100-Continue" Header if the content of a POST request exceeds 1024 bytes.

At least since 2003 SUN refuses to add support for this header to the servlet API. Java web application inside servlet containers have no ability to control 100 Continue responses.

Most servlet container implementations will immediately send this response whenever an "Expect: 100-Continue" is received.

Answer 2

The .net System.Net.HttpWebRequest sends an Expect: 100-continue on every post request by default. Tomcat, at least, sends a 100-continue before executing the servlet.