} } class ClientHandler extends Thread { private Socket client; private Scanner input; private PrintWriter output;

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1 import java.io.*; import java.net.*; import java.util.*; import java.util.properties; public class WebServer private static ServerSocket serversocket; private static final int PORT = 1234; public static void main(string[] args) throws IOException serversocket = new ServerSocket(PORT); catch (IOException ioex) System.out.println("\nUnable to set up port!"); System.exit(1); do //Wait for client... Socket client = serversocket.accept(); System.out.println("New client accepted.\n"); //Create a thread to handle communication with //this client and pass the constructor for this //thread a reference to the relevant socket... ClientHandler handler = new ClientHandler(client); handler.start();//as usual, method calls run. while (true); class ClientHandler extends Thread private Socket client; private Scanner input; private PrintWriter output; protected static final int RQ_INVALID = 0, RQ_GET = 1, RQ_POST = 2; private static Hashtable cache = new Hashtable(); protected final static String DEF_NAME = "/index.html"; public ClientHandler(Socket socket) //Set up reference to associated socket... client = socket; input = new Scanner(client.getInputStream()); output = new PrintWriter(client.getOutputStream(),true); catch(ioexception ioex) Web server / 5

2 ioex.printstacktrace(); public void run() String received,filename, response,content_file; String []MSG; Scanner readfromfile; int methodtype = RQ_INVALID; System.out.println("Opening connection... "); //Accept message from client onthe socket's input stream... received = input.nextline(); // Use a StringTokenizer to break the request into its three parts: // HTTP method, resource name, and HTTP version StringTokenizer st = new StringTokenizer(received); if (st.counttokens()!= 3) errorresponse(444, "Unparseable input " + received); String rqcode = st.nexttoken(); String rqname = st.nexttoken(); String rqhttpver = st.nexttoken(); System.out.println("Request: Command " + rqcode +", file " + rqname + ", version " + rqhttpver); // Read headers, up to the null line before the body, // so the body can be read directly if it's a POST. HashMap<String, String> map = new HashMap<String, String>(); String hdrline; while ((hdrline = input.nextline())!= null && hdrline.length()!= 0) int ix; if ((ix=hdrline.indexof(':'))!= -1) String hdrname = hdrline.substring(0, ix); String hdrvalue = hdrline.substring(ix+1).trim(); map.put(hdrname, hdrvalue); else System.err.println("INVALID HEADER: " + hdrline); // check that rqcode is either GET or POST if ("get".equalsignorecase(rqcode)) methodtype = RQ_GET; else if ("post".equalsignorecase(rqcode)) methodtype = RQ_POST; else errorresponse(400, "invalid method: " + rqcode); Web server / 5

3 dofile(rqname, output); catch(ioexception ioex) ioex.printstacktrace(); output.flush(); //Rendering the page if (client!=null) System.out.println("Closing down connection..."); client.close(); catch(ioexception ioex) System.out.println("Unable to disconnect!"); /** Sends an error response, by number, hopefully localized. */ protected void errorresponse(int errnum, String errmsg) // Check for localized messages ResourceBundle messages = ResourceBundle.getBundle("errors"); String response; response = messages.getstring(integer.tostring(errnum)); catch (MissingResourceException e) response=errmsg; // Generate and send the response output.println("http/1.0 " + errnum + " " + response); output.println("content-type: text/html"); output.println(); output.println("<html>"); output.println("<head><title>error " + errnum + "--" + response + "</title></head>"); output.println("<h1>" + errnum + " " + response + "</h1>"); sendend(); /** Send the tail end of any page we make up. */ protected void sendend() output.println("<hr>"); output.println("<address>java Web Server,"); String myaddr = " output.println("<a href=\"" + myaddr + "\">" + myaddr + "</a>"); output.println("</address>"); output.println("</html>"); output.println(); Web server / 5

4 public String DecodeURL(String pth) StringBuilder sb = new StringBuilder(); char[] UrlCharArray = pth.tochararray(); for (int i = 0; i < UrlCharArray.length; i++) if (UrlCharArray[i] == '%' && UrlCharArray[i+1] == '2' && UrlCharArray[i+2] == '0') sb.append(" "); i+=2; else sb.append(urlchararray[i]); return sb.tostring(); /** Processes one file request */ void dofile(string rqname, PrintWriter os) throws IOException rqname=decodeurl(rqname); System.out.println("C:/java/lab3/htdocs" + rqname); File f; byte[] content = null; Object o = cache.get(rqname); if (o!= null && o instanceof byte[]) content = (byte[])o; System.out.println("Using cached file " + rqname); sendfile(rqname, content, os); else if ((f = new File( "C:/java/lab3/htdocs" + rqname)).isdirectory()) // Directory with index.html? Process it. File index = new File(f, DEF_NAME); if (index.isfile()) dofile(rqname + DEF_NAME, index, os); else // Directory? Do not cache; always make up dir list. System.out.println("DIRECTORY FOUND"); dodirlist(rqname, f, os); sendend(); else if (f.canread()) // REGULAR FILE dofile(rqname, f, os); else errorresponse(404, "File not found"); void dodirlist(string rqname, File dir, PrintWriter os) if(rqname.equals("/")) rqname="/."; os.println("http/ directory found"); os.println("content-type: text/html"); os.println("date: " + new Date().toString()); os.println(""); os.println("<html>"); os.println("<title>contents of directory " + rqname + "</TITLE>"); os.println("<h1>contents of directory " + rqname + "</H1>"); Web server / 5

5 String fl[] = dir.list(); Arrays.sort(fl); for (int i=0; i<fl.length; i++) os.println("<br/><a href=\"" + rqname + File.separator + fl[i] + "\">" + "<img align='center' border='0' src=\"/icons/file.gif\">" + ' ' + fl[i] + "</a>"); /** Send one file, given a File object. */ void dofile(string rqname, File f, PrintWriter os) throws IOException System.out.println("Loading file " + rqname); InputStream in = new FileInputStream(f); byte c_content[] = new byte[(int)f.length()]; // Single large read, should be fast. int n = in.read(c_content); cache.put(rqname, c_content); sendfile(rqname, c_content, os); in.close(); /** Send one file, given the filename and contents. justhead - if true, send heading and return. */ void sendfile(string fname, byte[] content, PrintWriter os) throws IOException os.println("http/ Here's your file"); os.println("content-type: " + guessmime(fname)); os.println("content-length: " + content.length); os.println(); os.println(new String(content)); /** The type for unguessable files */ final static String UNKNOWN = "unknown/unknown"; protected String guessmime(string fn) ResourceBundle messages = ResourceBundle.getBundle("mime"); String lcname = fn.tolowercase(); int extenstartsat = lcname.lastindexof('.'); if (extenstartsat<0) if (fn.equalsignorecase("makefile")) return "text/plain"; return UNKNOWN; String exten = lcname.substring(extenstartsat); String guess ; guess = messages.getstring(exten); catch (MissingResourceException e) guess ="text/plain"; return guess; Web server / 5

Distributed Systems COMP 212. Lecture 8 Othon Michail

Distributed Systems COMP 212. Lecture 8 Othon Michail Distributed Systems COMP 212 Lecture 8 Othon Michail HTTP Protocol Hypertext Transfer Protocol Used to transmit resources on the WWW HTML files, image files, query results, Identified by Uniform Resource