Hypertext Transfer Protocol

1. Communication Process:

• Browser -> DNS Server -> (IP) Browser
• Browser -> (TCP/IP) Web Server [SYN connection] -> Browser [SYN-ACK connection] -> Web Server [ACK]
• Browser -> (HTTP request) Web Server -> (HTTP response) Browser

2. Ports:

• Telnet: 23
• SMTP: 25
• MySQL: 3306

For web servers:

• Deployment:
  • HTTP: 80
  • HTTPS: 443
• Development:
  • HTTP: 8000 or 8080
  • HTTPS: 8843

3. HTTP Request:

Methods:

• Safe:
  • GET, HEAD, TRACE, OPTIONS
• Idempotent:
  • PUT, DELETE (allowed to change the server, can have side effects, but multiple options should have the same effect as once)
• Update:
  • POST (arbitrary changes)

HTTP Methods:

• GET:

  • To retrieve data. Can be cached. URL length is less than 2048 characters. Only ASCII.
  • Example: /test/demo_form.asp?name1=value1&name2=value2

• POST:

  • To post data. Cannot be cached. No length limitation. Supports all types (including binary).
  • Example:

    POST /test/demo_form.asp HTTP/1.1  
    Host: w3schools.com  
    name1=value1&name2=value2

• HEAD:

  • Similar to GET, but only responds with the HTTP header, without the body.

• PUT:

  • Upload URI.
  • Example: http://blog.csdn.net/yangruibao/article/details/7898788

• DELETE:

  • Delete resource.

• OPTIONS:

  • Response supported HTTP methods.

• CONNECT:

  • Changes connection to TCP/IP.

4. HTTP Response:

Response Headers:

• Content-Type, Content-Length, etc.

Response Body:

• The content is a sequence of bytes with an associated MIME type.
  Example: \r\n (carriage return and newline).