Java Tutorial/Network/HTTP Server

Grabbing a page using socket

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();
  }
}

Lightweight HTTP Server

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();
    }
  }
}

POSTing data to an HTTP server

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();
  }
}

Sending a POST Request Using a Socket

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();
  }
}

Web ping

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();
  }
}