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Tilman
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// Netzprogrammierung
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// Gruppe 01 (Übung 1)
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// Aufgabe 1-4
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/*
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ProxyServer.java
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Anmerkungen:
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- Dem Proxyserver können auf der Kommandozeile optional Port und Debug Level als int-Werte
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übergeben werden (Silent Mode, nur Header, etc.). Als default werden Port 10000 und Debug
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Level 3 genutzt.
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Konzepte:
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- Die Eingabeströme von Client und v.a. Server werden über binäre Inputstreams abgewickelt,
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um Bilder und andere Binärdaten zu erhalten
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- Aus dem Client-Request werden Server und Port geparst, so kann bspw. auch http über Port
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8080 abgefragt werden
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- Der vom Client entgegengenommene Header wird teilweise bereinigt, da er sich an einen
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Proxy richtet (Zeile 148 ff.)
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- Die Antwort vom Server wird über die private Methode readLine() (Z. 242 ff.) abgewickelt, so
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kann der InputStream komfortabel gehandhabt werden
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- Die empfangenen Headerzeilen werden aufsummiert und durch die angeforderten Ressourcen
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geteilt. Das Ergebnis wird über den Header an den Client gesendet (Z. 190 ff.)
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- Die meisten Exceptions werden nur abgefangen, der Proxyserver läuft danach wieder an, da
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die meisten Fehler durch Abbruch der Verbindung durch den Client u.ä. entstehen, bemerkt
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man dies im Betrieb i.d.R. nicht
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- Die einzige gesondert behandelte Exception ist die Connection Exception (Z. 214): Tritt sie
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auf, wird HTTP-Fehlercode 500 an den Client übermittelt
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*/
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package uebung01.aufgabe04;
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import java.io.BufferedInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.PrintStream;
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import java.net.ConnectException;
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import java.net.ServerSocket;
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import java.net.Socket;
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import java.net.SocketException;
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import java.net.SocketTimeoutException;
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import java.util.Iterator;
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import java.util.LinkedList;
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/**
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* Ein einfacher Proxy-Server, der die durchschnittliche Anzahl empfangener Headerzeilen ermittelt.
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*
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* @author Tilman Walther
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*/
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public class ProxyServer {
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// da unser einfacher Proxy die content-length nicht beruecksichtigt (die
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// auch nicht von jedem Server gesendet wird), muessen Verbindungen oft
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// per Timeout beendet werden.
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final int SERVER_TIMEOUT = 2500;
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// da Java den Linefeed dem System anpasst, nutzen wir einen
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// String, der sich nach dem HTTP-Protokoll richtet
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final String LF = new String(""+((char) 13)+((char) 10));
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long headerLineCount = 0;
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long itemCount = 0;
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StringBuffer lineBuffer = new StringBuffer(600);
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public ProxyServer(int port, int message) throws IOException {
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System.out.println("PROXY: Starting ProxyServer on port "+port);
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ServerSocket proxySocket = new ServerSocket(port);
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Socket client;
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BufferedInputStream clientIn;
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PrintStream clientOut;
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Socket server;
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BufferedInputStream serverIn;
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PrintStream serverOut;
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String request;
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String domain;
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int serverport;
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LinkedList requestStrings = new LinkedList();
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String s;
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byte[] buffer = new byte[1024];
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int in1;
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long headerLineAverage;
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while (true) {
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if (message > 1) System.out.println("PROXY: Listening... (press Ctrl+C to end)");
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client = proxySocket.accept();
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clientIn = new BufferedInputStream(client.getInputStream());
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clientOut = new PrintStream(client.getOutputStream(), true);
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try {
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// Anfrage vom Browser holen
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s = readLine(clientIn);
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// Ressource extrahieren
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request = s.substring(0, s.indexOf(" ")+1) + s.substring(s.indexOf("/", s.indexOf("//")+2));
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// Domain und Port extrahieren
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domain = s.substring(s.indexOf("//")+2);
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domain = domain.substring(0, domain.indexOf("/"));
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if ((in1 = domain.indexOf((int) ':')) > -1 ) {
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serverport = Integer.parseInt(domain.substring(in1+1));
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domain = domain.substring(0, in1);
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}
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else {
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serverport = 80;
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}
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if (message > 1) System.out.print("PROXY: Request from client: "+s);
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// Restlichen Anfrage-Header holen
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requestStrings.clear();
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do {
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s = readLine(clientIn);
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requestStrings.add(s);
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if (message > 4) System.out.print(" "+s);
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} while (!s.equals(LF));
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long time = System.currentTimeMillis();
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try {
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if (message > 1) System.out.println("PROXY: Connecting server "+domain+":"+serverport);
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server = new Socket(domain, serverport);
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server.setSoTimeout(SERVER_TIMEOUT);
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serverIn = new BufferedInputStream(server.getInputStream());
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serverOut = new PrintStream(server.getOutputStream(), true);
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if (message > 1) System.out.print("PROXY: Sending request to server: "+request);
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serverOut.print(request);
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// Angepassten Header an Server schicken
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Iterator iter = requestStrings.iterator();
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while (iter.hasNext()) {
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s = (String) iter.next();
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if (s.startsWith("Proxy-Connection")) {
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serverOut.print("Connection: close"+LF);
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if (message > 2) System.out.print(" Connection: close"+LF);
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}
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else if (s.startsWith("Transfer-Encoding")) {
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serverOut.print("Transfer-Encoding: identity"+LF);
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if (message > 2) System.out.print(" Transfer-Encoding: identity"+LF);
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}
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else if (s.startsWith("Accept-Encoding")) {
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s = s.substring(0,(s.length()-2)).concat(",identity"+LF);
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//s = "Accept-Encoding: identity"+LF;
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serverOut.print(s);
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if (message > 2) System.out.print(" "+s);
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}
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else {
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serverOut.print(s);
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if (message > 2) System.out.print(" "+s);
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}
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}
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// Antwort vom Server entgegennehmen
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try {
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// Header empfangen
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s = readLine(serverIn);
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// --> Hier koennen HTTP response codes abgefangen werden
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if (message > 1) System.out.print("PROXY: Receiving data from server: "+s);
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itemCount++;
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while (!s.equals(LF)) {
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headerLineCount++;
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if (message > 2) System.out.print(" "+s);
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clientOut.print(s);
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s = readLine(serverIn);
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}
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// durchschnittliche Anzahl der Headerzeilen berechnen
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headerLineAverage = headerLineCount / itemCount;
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if (message > 2) System.out.print(" X-mean-headercount: "+ headerLineAverage + LF + LF);
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clientOut.print("X-mean-headercount: "+ headerLineAverage + LF + LF);
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// Daten empfangen
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while ((in1 = serverIn.read(buffer)) > 0) {
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if (message > 3) System.out.write(buffer, 0, in1);
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clientOut.write(buffer, 0, in1);
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}
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}
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catch (SocketTimeoutException ste) {
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if (message > 1) System.err.println("PROXY: Connection timed out");
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}
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if (message > 1) System.out.println("PROXY: Time "+(System.currentTimeMillis()-time)+" ms");
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if (message > 1) System.out.println("PROXY: Unconnect...\n");
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serverIn.close();
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serverOut.close();
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server.close();
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}
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catch (ConnectException ce) {
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if (message > 0) System.err.println("ConnectException, sending code 500 to client");
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buffer = ("HTTP/1.0 500\nContent Type: text/plain\n\nError while connecting server: "+domain+"\n").getBytes();
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clientOut.write(buffer, 0, ("HTTP/1.0 500\nContent Type: text/plain\n\nError while connecting server: "+domain+"\n").length());
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}
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clientIn.close();
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clientOut.close();
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client.close();
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}
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catch (SocketException se) {
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if (message > 4) System.err.println("SocketException");
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}
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catch (Exception e) {
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// nothing, just try again
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if (message > 4) e.printStackTrace();
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}
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}
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//proxySocket.close();
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}
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/**
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* Liest eine Zeile vom binären Eingabestrom.
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* (Auf diese Weise bleiben binäre Daten korrekt erhalten.)
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*/
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private String readLine(InputStream in) throws IOException
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{
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int i;
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lineBuffer.setLength(0);
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while (((i = in.read()) > 0) && (i != 13)){
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lineBuffer.append((char) i);
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}
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// nach HTTP 1.1 müssten die Zeilenenden mit #13#10 markiert sein
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// (durch die Aufteilung schlucken wir auch Unix/Macintosh)
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if (i == 13) {
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lineBuffer.append((char) 13);
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in.mark(1);
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if (in.read() != 10)
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in.reset();
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else
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lineBuffer.append((char) 10);
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}
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return lineBuffer.toString();
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}
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public static void main(String[] args) throws IOException {
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int port = 10000; // default port
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int message = 3; // default output level
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if (args.length > 2) {
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System.out.println("usage: MultServer [port number] [output level]");
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}
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else {
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if (args.length > 0) {
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try {
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port = Integer.parseInt(args[0]);
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}
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catch (NumberFormatException nfe) {
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System.out.println(args[0]+" is not a valid port number.\nusage: MultServer [port number] [output level]");
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System.exit(1);
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}
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}
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if (args.length > 1) {
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try {
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port = Integer.parseInt(args[1]);
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}
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catch (NumberFormatException nfe) {
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System.out.println(args[0]+" is not a valid port number.\nusage: MultServer [port number] [output level]");
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System.exit(1);
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}
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}
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}
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new ProxyServer(port, message);
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}
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}
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