iOS development: Get and POST requests in HTTP

What is HTTP?

The Hypertext Transfer Protocol (HTTP) is designed to ensure communication between the client and the server.

HTTP works as a request-response protocol between the client and the server.

A Web browser might be a client, and a network application on a computer might be a server-side.

Example: the client (browser) submits an HTTP request to the server, and the server returns a response to the client. The response contains status information about the request and what might be requested.

Two methods of HTTP request: GET and POST

In the request-response between the client and the server, the two most commonly used methods are: GET and POST.

• GET -requests data from the specified resource.
• POST -submits the data to be processed to the specified resource.

GET method

Note that the query string (name/value pair) is sent in the URL of the GET request:

/test/demo_form.php ? name1=value1&name2=value2

Some additional comments about the GET request:

• Get requests can be cached
• GET requests remain in browser history
• Get requests can be bookmark-Favorites
• GET requests should not be used when handling sensitive data
• Get request has a length limit
• GET requests should only be used to retrieve data

POST method

Note that the query string (name/value pair) is sent in the HTTP message body of the POST request:

post/test/demo_form.php http/1.1
Host:w3cschool.cc
name1=value1&name2=value2

Some additional comments about the POST request:

• POST requests are not cached
• POST requests are not persisted in browser history
• POST cannot be bookmarked
• POST request has no requirement for data length

Compare GET to POST

The following table compares the two HTTP methods: GET and POST.

	GET	POST
Back button/Refresh	Harmless	The data is resubmitted (the browser should tell the user that the data will be resubmitted).
Bookmark	Bookmark can be bookmarked	Bookmark not available for collection
Cache	can be cached	Cannot be cached
Encoding type	application/x-www-form-urlencoded	Application/x-www-form-urlencoded or Multipart/form-data. Use multiple encodings for binary data.
History	The parameters remain in the browser history.	Parameters are not saved in the browser history.
Limits on the length of data	Yes. When data is sent, the GET method adds data to the URL, and the length of the URL is limited (the maximum length of the URL is 2048 characters).	Unlimited.
Restrictions on data types	Only ASCII characters are allowed.	There is no limit. Binary data is also allowed.
Security	GET is less secure than POST because the data being sent is part of the URL. Never use GET when sending passwords or other sensitive information!	POST is more secure than GET because parameters are not saved in the browser history or Web server logs.
Visibility of	The data is visible to everyone in the URL.	The data is not displayed in the URL.

Other HTTP Request Methods

Some other HTTP request methods are listed in the following table:

Method	Description
HEAD	Same as GET, but returns only the HTTP header and does not return the document body.
PUT	Uploads the specified URI representation.
DELETE	Deletes the specified resource.
OPTIONS	Returns the HTTP methods supported by the server.
CONNECT	Convert the request connection to a transparent TCP/IP channel.

iOS development: Get and POST requests in HTTP