The Web is established through the use of HTTP. The data transmission between Web Servers and Web Browsers is performed through HTTP. The data send from a Web Browser to a Web Server is called a "request," and the data sent from a Web Server to a Web Browser is called a "response." Generally, a response must exist for each request. A communication path is assured by the request, and released when a response is completed. For HTTP, the request and response have the same format except the first line, which have very simple formats as shown below.
Request Data
Method URL version |
HTTP header |
Message body |
Response Data
Version Status code Reason |
HTTP header |
Message body |
The following explains each of the terms used in the above tables:
Indicates the contents of a request to a Web Server, which include GET, POST, and HEAD.
Indicates the location of a resource to be requested.
Indicates the version of HTTP to be used.
Indicates the condition of processing by the server or Web application, which is represented in 3 digits.
The reason for the status code.
Used to control Web Browser from Web Server, or to add the conditions to the Web Browser information or method.
Indicates the data to be transmitted between a Web Server and a Web Browser.
For details of these terms, refer to the specifications or books about HTTP. This appendix briefly explains the method, status code, and HTTP header that are referred to or set up by Web applications.
The following lists the main methods:
This method fetches the information specified in URL. When the information specified in URL is a Web application (an executable file name and optional input parameters), this method resends the data output by the Web application.
There is an upper limit to the amount of data that the Web server can receive through the data input to the form that is passed to the application.
This method is functionally the same as GET, but different from GET in the respect that only the HTTP header is resent. This method is used for checking the attribute of the information specified in a URL.
This method is used for sending the data input from forms, to the Web application. GET functions similar to POST, but the quantity of data transmitted by GET is upper-limited.
Status code | Explanation |
|---|---|
200 | Normal end |
302 | The requested document was temporarily moved. For the location where it was moved, refer to the "Location" header. |
303 | The requested document was moved to a different URL. For the location where it was moved, refer to the "Location" header. |
400 | Syntax error |
401 | Authorization has failed. |
403 | Accessing the specified URL is inhibited. |
404 | There is no resource for the requested URL. |
410 | There is a resource inconsistent between the Web Browser and Server. |
500 | Internal error. For example, when no response is sent from Web applications. |
502 | An invalid request was returned from the Web Server. |
503 | Web Server cannot be accessed because of high load. |
HTTP header | Explanation |
|---|---|
Accept | Indicates the MIME type that Web Browser can received. |
Accept-Charset | Indicates the character code set that Web Browser can received. |
Accept-Encoding | Encoding format that Web Browser can received, which generally indicates the data compression format. |
Accept-Language | Indicates the language type that Web Browser can received. The national language is represented as "ja" and English is represented as "en." |
Content-Encoding | Indicates the encoding format of the response data. |
Content-Language | Indicates the language type of the response data. |
Content-Type | Indicates the MIME type of the response data. |
Date | Indicates the date when the request data or response data has been created. |
Expires | Indicates the term of validity for the response data. |
Location | Indicates the correct location where the information is stored. |
Host | Host name of the server where Web Server is operated. |
Referer | Indicates the requesting URL. |
User-Agent | Indicates the Web Browser information. |
