Controlling HTTP Response Header Lines

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HTTP Response Syntax

Based on HTTP/1.1 protocol, after receiving and interpreting an HTTP request from a client, a server must responds with an HTTP response following the syntax bellow:

status-line
header-line
...
header-line

entity-body

Note that:

• Response must have one status-line.
• Response can have zero, one, or many header lines.
• Response can only have zero or one entity-body.
• There is a blank line between header lines and the entity body.
• Status line, head line, and blank line must be ended with CRLF ("/r/n") characters.
• Entity body is the actual data requested by the client request.
• Header lines can be in any order.

Bellow is a simple HTTP response with two header lines:

HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 38

Hello world!

HTTP Response Header Lines

HTTP/1.1 response header lines allows the server to passes additional information about the response which cannot be placed in the status line. Header lines can be divided into three groups:

1. General header lines: Information about the transmission of the entire response message:

   Cache-Control      
   Connection         
   Date               
   Pragma             
   Trailer            
   Transfer-Encoding  
   Upgrade            
   Via                
   Warning          

2. Response header lines: Information about the response:

   Accept-Ranges     
   Age               
   ETag              
   Location          
   Proxy-Authenticate
   Retry-After       
   Server            
   Vary              
   WWW-Authenticate

3. Entity header lines: Information about the data requested by the client:

   Allow              
   Content-Encoding   
   Content-Language   
   Content-Length     
   Content-Location   
   Content-MD5        
   Content-Range      
   Content-Type       
   Expires            
   Last-Modified      

(Continued on next part...)

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