Here is some sample Java code that demonstrates how to create and run a simple web server:
import java.io.*;
import java.net.*;
public class WebServer {
public static void main(String[] args) throws IOException {
// Set the port number
int port = 8080;
// Establish the listen socket
ServerSocket serverSocket = new ServerSocket(port);
// Process HTTP service requests in an infinite loop
while (true) {
// Listen for a TCP connection request
Socket connectionSocket = serverSocket.accept();
// Construct an object to process the HTTP request message
HttpRequest request = new HttpRequest(connectionSocket);
// Create a new thread to process the request
Thread thread = new Thread(request);
// Start the thread
thread.start();
}
}
}
final class HttpRequest implements Runnable {
final static String CRLF = “\r\n”;
Socket socket;
// Constructor
public HttpRequest(Socket socket) throws Exception {
this.socket = socket;
}
// Implement the run() method of the Runnable interface
public void run() {
try {
processRequest();
} catch (Exception e) {
System.out.println(e);
}
}
private void processRequest() throws Exception {
// Get a reference to the socket’s input and output streams
InputStream is = socket.getInputStream();
DataOutputStream os = new DataOutputStream(socket.getOutputStream());
// Set up input stream filters
BufferedReader br = new BufferedReader(new InputStreamReader(is));
// Get the request line of the HTTP request message
String requestLine = br.readLine();
// Extract the filename from the request line
String[] requestTokens = requestLine.split(” “);
String fileName = requestTokens[1];
// Prepend a “.” so that file request is within the current directory.
fileName = “.” + fileName;
// Open the requested file.
FileInputStream fis = null;
boolean fileExists = true;
try {
fis = new FileInputStream(fileName);
} catch (FileNotFoundException e) {
fileExists = false;
}
// Construct the response message
String statusLine = null;
String contentTypeLine = null;
String entityBody = null;
if (fileExists) {
statusLine = “HTTP/1.0 200 OK” + CRLF;
contentTypeLine = “Content-type: “ +
contentType(fileName) + CRLF;
} else {
statusLine = “HTTP/1.0 404 Not Found” + CRLF;
contentTypeLine = “Content-type: text/html” + CRLF;
entityBody = “<HTML>” +
“<HEAD><TITLE>Not Found</TITLE></HEAD>” +
“<BODY>Not Found</BODY></HTML>”;
}
// Send the status line
os.writeBytes(statusLine);
// Send the content type line
os.writeBytes(contentTypeLine);
// Send
// Send the entity body
if (fileExists) {
sendBytes(fis, os);
fis.close();
} else {
os.writeBytes(entityBody);
}
// Close streams and socket
os.close();
br.close();
socket.close();
}
private static void sendBytes(FileInputStream fis, OutputStream os) throws Exception {
// Construct a 1K buffer to hold bytes on their way to the socket.
byte[] buffer = new byte[1024];
int bytes = 0;
// Copy requested file into the socket’s output stream.
while((bytes = fis.read(buffer)) != –1 ) {
os.write(buffer, 0, bytes);
}
}
private static String contentType(String fileName) {
if(fileName.endsWith(“.htm”) || fileName.endsWith(“.html”)) {
return “text/html“;
}
if(fileName.endsWith(“.jpg”) || fileName.endsWith(“.jpeg”)) {
return “image/jpeg”;
}
if(fileName.endsWith(“.gif”)) {
return “image/gif”;
}
return “application/octet-stream”;
}
}
This code creates a simple web server that listens for HTTP requests on port 8080. When it receives a request, it responds with the requested file if it exists, or a “404 Not Found” error message if the file does not exist. The code uses the `java.net` and `java.io` packages to handle networking and input/output tasks. To use this code, you will need to compile it and then run the `WebServer` class.
The web server will then start listening for requests on port 8080. You can test the server by opening a web browser and navigating to `http://localhost:8080/` followed by the name of a file in the current directory. For example, if you have a file called `index.html` in the current directory, you can access it by navigating to `http://localhost:8080/index.html` in your web browser.
