[Reserved] Implement a web server with Java

Hypertext Transfer Protocol (HTTP) is an application layer in TCP / IP protocol, which is the most widely known protocol, which is also one of the most core protocols in the interconnect. Similarly, HTTP is also implemented based on C / S or B / S model. In fact, our browser such as Netscape or IE is a client in the HTTP protocol, and some common web server software such as Apache, IIS, and IPlanet Web Server are server-only in the HTTP protocol. The web page is positioned by the server resource, transferred to the browser. After the browser explains, it is seen by the customer.

The WEB's work is based on the client / server computing model, consisting of a web browser (client), and web server (server), and the Hypertext Transfer Protocol (HTTP) is communicated between the two. The HTTP protocol is an application layer protocol between web browsers and web servers, which is a general, stateless, object-oriented protocol.

A complete HTTP protocol session process includes four steps:

◆ Connection, the web browser establishes a connection to the web server, open a virtual file called Socket (socket), and the establishment of this file is successful;

◆ Request, the web browser submits a request to the web server via Socket. HTTP's request is typically a get or post command (POST is used for the transfer of the FORM parameter);

◆ Acknowledges that the web browser submits the request, transferred to the web server via the HTTP protocol. After the web server is connected, transaction processing, the processing result is sent back to the web browser via HTTP, so that the requested page is displayed on the web browser;

◆ Close the connection, the web browser and the web server must be disconnected after the response is completed to ensure that other web browsers can connect with the web server.

Programming ideas

According to the session process of the above HTTP protocol, the method of implementing the web server program of the GET request is implemented, and the method is as follows:

By creating a Serversocket class object, listen to the port (8080) specified by the user, wait and accept the client request to the port. Create the input stream and output stream associated with the socket, and then read the client's request information. If the request type is Get, get the HTML file name accessed from the request information; if the HTML file exists, open the HTML file, transfer the HTTP header information and the HTML file content to the web browser via Socket, then close the file, then close the file, Otherwise send an error message to the web browser. Finally close the socket connected to the corresponding web browser.

Write the source code of the web server httpserver.java file with Java as follows:

//httpserver.java

Import java.net. *;

Import java.io. *;

Import java.util. *;

Import java.lang. *;

Public clas httpserver {

Public static void main (string args []) {

Int port;

Serversocket Server_Socket;

// Read server port number

Try {

Port = integer.parseint (args [0]);

}

Catch (Exception E) {

Port = 8080;

}

Try {

// listen to the server port, wait for the connection request

Server_socket = new serversocket (port);

System.out.println ("Httpserver Running on Port" Server_Socket.getlocalPort ());

// Display startup information

While (true) {

Socket Socket = Server_Socket.accept ();

System.out.println ("New Connection ACCEPTED"

Socket.getinetaddress ()

":" Socket.getPort ());

// Create a division thread

Try {

HttpRequestHandler Request =

New httprequesthandler (socket);

Thread thread = new three (request);

// Start thread

Thread.start ();

}

Catch (Exception E) {

System.out.println (e);

}

}

}

Catch (IOException E) {

System.out.println (e);

}

}

}

Class HttpRequestHandler Implements Runnable

{

Final static string crlf = "/ r / n";

Socket socket;

InputStream INPUT;

OutputStream output;

BUFFEREDReader Br;

// Construction method

Public HttpRequestHandler (Socket Socket) Throws Exception

{

This.socket = Socket;

This.input = Socket.getinputStream ();

this.output = socket.getOutputStream ();

THIS.BR =

New BufferedReader (new input.getinputstream ()));

}

/ / Realize the Run () method of the runnable interface

Public void Run ()

{

Try {

PROCESSREQUEST ();

}

Catch (Exception E) {

System.out.println (e);

}

}

Private Void ProcessRequest () THROWS Exception

{

While (true) {

/ / Read and display the request information submitted by the web browser

String headerline = br.readline ();

System.out.println ("The Client Request IS" HeaderLine);

IF (HeaderLine.equals (CRLF) || HeaderLine.equals (")) Break;

StringTokenizer S = New StringTokenizer (HeaderLine);

String Temp = S.NEXTTOKEN ();

IF (Temp.equals ("Get")) {

String filename = S.NEXTTOKEN ();

Filename = "." filename;

/ / Open the requested file

FileInputStream Fis = NULL;

Boolean FileExists = true;

Try

{

FIS = New FileInputStream (FileName);

}

Catch (FilenotFoundException E)

{

FileExists = false;

}

/ / Complete the response message

String ServerLine = "Server: a Simple Java httpserver";

String statusline = null;

String contenttypeline = null;

String EntityBody = NULL;

String contentthline = "error";

IF (FileExists)

{

StatusLine = "HTTP / 1.0 200 OK" CRLF;

ContentTypeline = "Content-Type:"

ContentType (FileName) CRLF;

ContentLengthline = "Content-Length:"

(New integer (fis.available ())). TOSTRING ()

CRLF;

}

Else

{

Statusline = "http / 1.0 404 not found" CRLF;

ContentTypeline = "text / html";

EntityBody = ""

"