When working with the HTTP protocol, you may encounter various status codes. One of these codes is "100 Continue." This status code is primarily designed for optimizing the sending of requests, especially in HTTP/1.1. For example, when a client needs to send large amounts of data, it may first send a preliminary request that only includes headers. If the server responds with a 100 Continue, it indicates that everything is okay, and it can then send the actual request body.
In this way, a server can inform a client that everything is fine up to this point and that it can proceed. This process is particularly useful when asking for large requests and the client wants to ensure that there are no issues with the request header that would lead to the rejection of the entire request.
However, this process is typically managed by clients and servers automatically, and you should only engage with it in special situations where you have a specific designed system behind you.
Points to consider include the fact that this status is used more often in the HTTP/1.1 protocol and may change in future versions, or in some cases, it may not be needed. However, when dealing with legacy clients and servers, it is generally considered good practice.
As a developer, it’s good to be familiar with this status, but there’s no need to spend too much time unless you’re working on sensitive system networks.
As an example usage of the HTTP 100 Continue status in standard HTTP communications:
POST /upload HTTP/1.1\r\nHost: www.example.com\r\nContent-Length: 348\r\nExpect: 100-continue\r\n\r\n[Data that will be sent after the response is received in the form of a 100 Continue]Explanation of the above code:
POST /upload HTTP/1.1 – This line indicates that the client intends to send data using the POST method to the server at /upload. Host: www.example.com – The Host header indicates to which domain the request should be sent. Content-Length: 348 – This amount shows the length of the body of the request, which is 348 bytes here. Expect: 100-continue – This tells the server that the client is expecting to receive a 100 Continue response before sending the actual body, indicating that the connection is still valid. [Data that will be sent after receiving the 100 Continue response] – This line signifies the data that will be sent after receiving the 100 status.