Java Tutorial/Network/HTTP Server

Grabbing a page using socket

   <source lang="java">

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileWriter; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.net.Socket; import java.net.URL; public class Main {

 public static void main(String[] args) throws Exception {
   String pageAddr = "http://www.google.ru/index.htm";
   URL url = new URL(pageAddr);
   String websiteAddress = url.getHost();
   String file = url.getFile();
   Socket clientSocket = new Socket(websiteAddress, 80);
   BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket
       .getInputStream()));
   OutputStreamWriter outWriter = new OutputStreamWriter(clientSocket.getOutputStream());
   outWriter.write("GET " + file + " HTTP/1.0\r\n\n");
   outWriter.flush();
   BufferedWriter out = new BufferedWriter(new FileWriter(file));
   boolean more = true;
   String input;
   while (more) {
     input = inFromServer.readLine();
     if (input == null)
       more = false;
     else {
       out.write(input);
     }
   }
   out.close();
   clientSocket.close();
 }

}</source>

Lightweight HTTP Server

   <source lang="java">

import java.io.IOException; import java.io.OutputStream; import java.net.InetSocketAddress; import java.util.Iterator; import java.util.List; import java.util.Set; import java.util.concurrent.Executors; import com.sun.net.httpserver.Headers; import com.sun.net.httpserver.HttpExchange; import com.sun.net.httpserver.HttpHandler; import com.sun.net.httpserver.HttpServer; public class HttpServerDemo {

 public static void main(String[] args) throws IOException {
   InetSocketAddress addr = new InetSocketAddress(8080);
   HttpServer server = HttpServer.create(addr, 0);
   server.createContext("/", new MyHandler());
   server.setExecutor(Executors.newCachedThreadPool());
   server.start();
   System.out.println("Server is listening on port 8080" );
 }

} class MyHandler implements HttpHandler {

 public void handle(HttpExchange exchange) throws IOException {
   String requestMethod = exchange.getRequestMethod();
   if (requestMethod.equalsIgnoreCase("GET")) {
     Headers responseHeaders = exchange.getResponseHeaders();
     responseHeaders.set("Content-Type", "text/plain");
     exchange.sendResponseHeaders(200, 0);
     OutputStream responseBody = exchange.getResponseBody();
     Headers requestHeaders = exchange.getRequestHeaders();
     Set<String> keySet = requestHeaders.keySet();
     Iterator<String> iter = keySet.iterator();
     while (iter.hasNext()) {
       String key = iter.next();
       List values = requestHeaders.get(key);
       String s = key + " = " + values.toString() + "\n";
       responseBody.write(s.getBytes());
     }
     responseBody.close();
   }
 }

}</source>

POSTing data to an HTTP server

   <source lang="java">

import java.io.DataInputStream; import java.io.DataOutputStream; import java.net.URL; import java.net.URLConnection; public class Main {

 public static void main(String[] args) throws Exception {
   URL url = new URL("http://localhost:8080/postedresults.jsp");
   URLConnection conn = url.openConnection();
   conn.setDoInput(true);
   conn.setDoOutput(true);
   conn.setUseCaches(false);
   conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
   DataOutputStream out = new DataOutputStream(conn.getOutputStream());
   String content = "CONTENT=HELLO JSP !&ONEMORECONTENT =HELLO POST !";
   out.writeBytes(content);
   out.flush();
   out.close();
   DataInputStream in = new DataInputStream(conn.getInputStream());
   String str;
   while (null != ((str = in.readUTF()))) {
     System.out.println(str );
   }
   in.close();
 }

}</source>

Sending a POST Request Using a Socket

   <source lang="java">

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import java.net.InetAddress; import java.net.Socket; import java.net.URLEncoder; public class Main {

 public static void main(String[] argv) throws Exception {
   String data = URLEncoder.encode("key1", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8");
   
   Socket socket = new Socket("127.0.0.1", 8080);
   String path = "/servlet";
   BufferedWriter wr = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF8"));
   wr.write("POST " + path + " HTTP/1.0\r\n");
   wr.write("Content-Length: " + data.length() + "\r\n");
   wr.write("Content-Type: application/x-www-form-urlencoded\r\n");
   wr.write("\r\n");
   wr.write(data);
   wr.flush();
   BufferedReader rd = new BufferedReader(new InputStreamReader(socket.getInputStream()));
   String line;
   while ((line = rd.readLine()) != null) {
     System.out.println(line);
   }
   wr.close();
   rd.close();
 }

}</source>

Web ping

   <source lang="java">

import java.net.InetAddress; import java.net.Socket; public class Main {

 public static void main(String[] args) throws Exception {
   InetAddress addr;
   Socket sock = new Socket(args[0], 80);
   addr = sock.getInetAddress();
   System.out.println("Connected to " + addr);
   sock.close();
 }

}</source>