This page contains the code for the proxy cache lab. You can copy the code into the correct files.
/**
* ProxyCache.java - Simple caching proxy
*
* $Id: ProxyCache.java,v 1.3 2004/02/16 15:22:00 kangasha Exp $
*
*/
import java.net.*;
import java.io.*;
import java.util.*;
public class ProxyCache {
/** Port for the proxy */
private static int port;
/** Socket for client connections */
private static ServerSocket socket;
/** Create the ProxyCache object and the socket */
public static void init(int p) {
port = p;
try {
socket = /* Fill in */;
} catch (IOException e) {
System.out.println("Error creating socket: " + e);
System.exit(-1);
}
}
public static void handle(Socket client) {
Socket server = null;
HttpRequest request = null;
HttpResponse response = null;
/* Process request. If there are any exceptions, then simply
* return and end this request. This unfortunately means the
* client will hang for a while, until it timeouts. */
/* Read request */
try {
BufferedReader fromClient = /* Fill in */;
request = /* Fill in */;
} catch (IOException e) {
System.out.println("Error reading request from client: " + e);
return;
}
/* Send request to server */
try {
/* Open socket and write request to socket */
server = /* Fill in */;
DataOutputStream toServer = /* Fill in */;
/* Fill in */
} catch (UnknownHostException e) {
System.out.println("Unknown host: " + request.getHost());
System.out.println(e);
return;
} catch (IOException e) {
System.out.println("Error writing request to server: " + e);
return;
}
/* Read response and forward it to client */
try {
DataInputStream fromServer = /* Fill in */;
response = /* Fill in */;
DataOutputStream toClient = /* Fill in */;
/* Fill in */
/* Write response to client. First headers, then body */
client.close();
server.close();
/* Insert object into the cache */
/* Fill in (optional exercise only) */
} catch (IOException e) {
System.out.println("Error writing response to client: " + e);
}
}
/** Read command line arguments and start proxy */
public static void main(String args[]) {
int myPort = 0;
try {
myPort = Integer.parseInt(args[0]);
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Need port number as argument");
System.exit(-1);
} catch (NumberFormatException e) {
System.out.println("Please give port number as integer.");
System.exit(-1);
}
init(myPort);
/** Main loop. Listen for incoming connections and spawn a new
* thread for handling them */
Socket client = null;
while (true) {
try {
client = /* Fill in */;
handle(client);
} catch (IOException e) {
System.out.println("Error reading request from client: " + e);
/* Definitely cannot continue processing this request,
* so skip to next iteration of while loop. */
continue;
}
}
}
}
/**
* HttpRequest - HTTP request container and parser
*
* $Id: HttpRequest.java,v 1.2 2003/11/26 18:11:53 kangasha Exp $
*
*/
import java.io.*;
import java.net.*;
import java.util.*;
public class HttpRequest {
/** Help variables */
final static String CRLF = "\r\n";
final static int HTTP_PORT = 80;
/** Store the request parameters */
String method;
String URI;
String version;
String headers = "";
/** Server and port */
private String host;
private int port;
/** Create HttpRequest by reading it from the client socket */
public HttpRequest(BufferedReader from) {
String firstLine = "";
try {
firstLine = from.readLine();
} catch (IOException e) {
System.out.println("Error reading request line: " + e);
}
String[] tmp = firstLine.split(" ");
method = /* Fill in */;
URI = /* Fill in */;
version = /* Fill in */;
System.out.println("URI is: " + URI);
if (!method.equals("GET")) {
System.out.println("Error: Method not GET");
}
try {
String line = from.readLine();
while (line.length() != 0) {
headers += line + CRLF;
/* We need to find host header to know which server to
* contact in case the request URI is not complete. */
if (line.startsWith("Host:")) {
tmp = line.split(" ");
if (tmp[1].indexOf(':') > 0) {
String[] tmp2 = tmp[1].split(":");
host = tmp2[0];
port = Integer.parseInt(tmp2[1]);
} else {
host = tmp[1];
port = HTTP_PORT;
}
}
line = from.readLine();
}
} catch (IOException e) {
System.out.println("Error reading from socket: " + e);
return;
}
System.out.println("Host to contact is: " + host + " at port " + port);
}
/** Return host for which this request is intended */
public String getHost() {
return host;
}
/** Return port for server */
public int getPort() {
return port;
}
/**
* Convert request into a string for easy re-sending.
*/
public String toString() {
String req = "";
req = method + " " + URI + " " + version + CRLF;
req += headers;
/* This proxy does not support persistent connections */
req += "Connection: close" + CRLF;
req += CRLF;
return req;
}
}
/**
* HttpResponse - Handle HTTP replies
*
* $Id: HttpResponse.java,v 1.2 2003/11/26 18:12:42 kangasha Exp $
*
*/
import java.io.*;
import java.net.*;
import java.util.*;
public class HttpResponse {
final static String CRLF = "\r\n";
/** How big is the buffer used for reading the object */
final static int BUF_SIZE = 8192;
/** Maximum size of objects that this proxy can handle. For the
* moment set to 100 KB. You can adjust this as needed. */
final static int MAX_OBJECT_SIZE = 100000;
/** Reply status and headers */
String version;
int status;
String statusLine = "";
String headers = "";
/* Body of reply */
byte[] body = new byte[MAX_OBJECT_SIZE];
/** Read response from server. */
public HttpResponse(DataInputStream fromServer) {
/* Length of the object */
int length = -1;
boolean gotStatusLine = false;
/* First read status line and response headers */
try {
String line = /* Fill in */;
while (line.length() != 0) {
if (!gotStatusLine) {
statusLine = line;
gotStatusLine = true;
} else {
headers += line + CRLF;
}
/* Get length of content as indicated by
* Content-Length header. Unfortunately this is not
* present in every response. Some servers return the
* header "Content-Length", others return
* "Content-length". You need to check for both
* here. */
if (line.startsWith(/* Fill in */) ||
line.startsWith(/* Fill in */)) {
String[] tmp = line.split(" ");
length = Integer.parseInt(tmp[1]);
}
line = fromServer.readLine();
}
} catch (IOException e) {
System.out.println("Error reading headers from server: " + e);
return;
}
try {
int bytesRead = 0;
byte buf[] = new byte[BUF_SIZE];
boolean loop = false;
/* If we didn't get Content-Length header, just loop until
* the connection is closed. */
if (length == -1) {
loop = true;
}
/* Read the body in chunks of BUF_SIZE and copy the chunk
* into body. Usually replies come back in smaller chunks
* than BUF_SIZE. The while-loop ends when either we have
* read Content-Length bytes or when the connection is
* closed (when there is no Connection-Length in the
* response. */
while (bytesRead < length || loop) {
/* Read it in as binary data */
int res = /* Fill in */;
if (res == -1) {
break;
}
/* Copy the bytes into body. Make sure we don't exceed
* the maximum object size. */
for (int i = 0;
i < res && (i + bytesRead) < MAX_OBJECT_SIZE;
i++) {
/* Fill in */
}
bytesRead += res;
}
} catch (IOException e) {
System.out.println("Error reading response body: " + e);
return;
}
}
/**
* Convert response into a string for easy re-sending. Only
* converts the response headers, body is not converted to a
* string.
*/
public String toString() {
String res = "";
res = statusLine + CRLF;
res += headers;
res += CRLF;
return res;
}
}