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Server.java
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Server.java
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/*
* Jinxing Wang (1468230) and Tad Perry (1340456)
*
* CSE 461 Project 1 Stage 1
*/
import java.io.*;
import java.net.*;
import java.nio.*;
import java.lang.*;
import java.util.*;
// This class handles the Server side of Project 1
public class Server {
private static Random randy = new Random();
private static final int TIMEOUT = 3000;
private static final int HEADER_LEN = 12;
private static final int START_PORT = 12235;
public static void main(String[] args) throws Exception {
Server s = new Server();
s.runServer();
}
// run server with muti thread
public void runServer() {
try {
DatagramSocket serverSocket = new DatagramSocket(START_PORT);
while(true){
byte[] buf = new byte[100];
DatagramPacket packetUDP = new DatagramPacket(buf, buf.length);
serverSocket.receive(packetUDP);
Thread thread = new Thread(new ServerConnection(serverSocket, packetUDP));
thread.start();
}
} catch (Exception e) { e.printStackTrace(); }
}
public class ServerConnection implements Runnable {
private InetAddress ipAddress;
private DatagramSocket socketUDP;
private DatagramPacket packetUDP;
private ServerSocket serverSock;
private Socket tcpSock;
private short sid;
private byte c;
private int tcpPort, port, len, num, secretA, secretB, secretC, secretD, pSecret = 0;
private void closeTCP() {
try {
serverSock.close();
tcpSock.close();
} catch (Exception e) {};
}
ServerConnection(DatagramSocket s, DatagramPacket p) {
socketUDP = s;
packetUDP = p;
}
// override run fun for thread to run
@Override
public void run () {
if (!stageA())
return;
pSecret = secretA;
if (!stageB())
return;
pSecret = secretB;
if (!stageC()) {
closeTCP();
return;
}
pSecret = secretC;
if (!stageD()) {
closeTCP();
return;
}
}
private boolean stageA() {
// in stage A right now
if (!checkHeader(packetUDP.getData(), 12, (short) 1))
return false;
ipAddress = packetUDP.getAddress();
xPacket p = new xPacket(ByteBuffer.wrap(packetUDP.getData()));
// start revieved message
bytesToHex(packetUDP.getData());
if ("hello world".equals(new String(p.payload).substring(0,11))
&& pSecret == p.secret)
{
sid = p.sid;
port = randy.nextInt(49151);
len = randy.nextInt(80);
num = randy.nextInt(10) + 1;
secretA = randy.nextInt();
ByteBuffer buf = ByteBuffer.allocate(16);
buf.putInt(num);
buf.putInt(len);
buf.putInt(port);
buf.putInt(secretA);
sendUDP(generatePacket((short) 2, buf.array(), buf.array().length), packetUDP.getPort());
return true;
}
return false;
}
private boolean stageB() {
// starting stage B
try {
socketUDP = new DatagramSocket(port);
//don't ack the first packet.
socketUDP.receive(packetUDP);
} catch (Exception e) {e.printStackTrace();}
ByteBuffer ackbuf = ByteBuffer.allocate(4);
int packetId = 0;
while (packetId < num) {
try { socketUDP.receive(packetUDP); } catch (Exception e) {e.printStackTrace();}
if (!checkHeader(packetUDP.getData(), len + 4, (short) 1))
return false;
xPacket pack = new xPacket(ByteBuffer.wrap(packetUDP.getData()));
if (checkPacket(pack, packetId, len + 4, (byte)0)) {
if (randy.nextInt(10) > 1) {
ackbuf.putInt(0, packetId++);
sendUDP(generatePacket((short) 1, ackbuf.array(), ackbuf.array().length), packetUDP.getPort());
}
}
else {
return false;
}
}
ByteBuffer buf = ByteBuffer.allocate(8);
tcpPort = randy.nextInt(49151);
secretB = randy.nextInt();
buf.putInt(tcpPort);
buf.putInt(secretB);
try {
serverSock = new ServerSocket(tcpPort);
serverSock.setSoTimeout(TIMEOUT);
} catch(Exception e) {e.printStackTrace(); return false;}
sendUDP(generatePacket((short) 2, buf.array(), buf.array().length), packetUDP.getPort());
return true;
}
private boolean stageC() {
// starting stage C
try {
// accepting tcpsocket
tcpSock = serverSock.accept();
} catch (Exception e) {
e.printStackTrace();
return false;
}
ByteBuffer buf = ByteBuffer.allocate(16);
len = randy.nextInt(80);
num = randy.nextInt(10) + 1;
secretC = randy.nextInt();
c = (byte) randy.nextInt(256);
buf.putInt(num);
buf.putInt(len);
buf.putInt(secretC);
buf.put(c);
try {
sendBytes(generatePacket((short) 2, buf.array(), 13));
} catch (Exception e) {e.printStackTrace();}
return true;
}
private boolean stageD() {
// staring stage D
xPacket pack = null;
try {
for (int i = 0; i < num; i++) {
byte[] res = readBytes((((HEADER_LEN + len) + 3) / 4) * 4);
if (res == null || !checkHeader(res, len, (short) 1))
return false;
pack = new xPacket(ByteBuffer.wrap(res));
// pack.print();
if (!checkPacket(pack, -1, len, c))
return false;
}
} catch (Exception e) {
e.printStackTrace();
return false;
}
secretD = randy.nextInt();
ByteBuffer buf = ByteBuffer.allocate(4);
buf.putInt(secretD);
sendBytes(generatePacket((short) 2, buf.array(), buf.array().length));
return true;
}
private byte[] generatePacket(short step, byte[] payload, int plength) {
int len = ((plength + 3) / 4) * 4;
ByteBuffer buf = ByteBuffer.allocate(HEADER_LEN + len);
buf.putInt(plength);
buf.putInt(pSecret);
buf.putShort(step);
buf.putShort(sid);
buf.put(payload);
return buf.array();
}
private boolean checkPacket(xPacket pack, int packetId, int expectedLength, byte c) {
ByteBuffer payload = ByteBuffer.wrap(pack.payload);
if (packetId > 0) {
int packId = payload.getInt();
if (packId != packetId)
return false;
}
for (int i = 0; i < len; i++)
if (payload.get() != c)
return false;
return true;
}
private boolean checkHeader(byte[] packet, int exPayloadLen, short exStep) {
// extract header
ByteBuffer header = ByteBuffer.allocate(12);
if(packet.length < 12)
return false;
byte[] subPacket = Arrays.copyOfRange(packet, 0, 12);
bytesToHex(subPacket);
header.put(subPacket);
// need to reset pointer
header.rewind();
int length = header.getInt();
if (length != exPayloadLen)
return false;
int secret = header.getInt();
if (secret != pSecret)
return false;
short step = header.getShort();
if (step != exStep)
return false;
return true;
}
public void sendUDP(byte[] sendData, int port) {
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, ipAddress, port);
// data are:
bytesToHex(sendData);
try {
socketUDP.send(sendPacket);
} catch (Exception e) {
e.printStackTrace();
}
}
public void sendBytes(byte[] bytes) {
try {
// sedning data here
bytesToHex(bytes);
OutputStream out = tcpSock.getOutputStream();
DataOutputStream dos = new DataOutputStream(out);
dos.write(bytes, 0, bytes.length);
dos.flush();
} catch (Exception e) {e.printStackTrace();}
}
public byte[] readBytes(int len) throws IOException {
InputStream in = tcpSock.getInputStream();
DataInputStream dis = new DataInputStream(in);
byte[] data = new byte[len];
try {
dis.readFully(data);
} catch(Exception e) {
return null;
}
return data;
}
private class xPacket {
public int length;
public int secret;
public short step;
public short sid;
public byte[] payload;
xPacket(ByteBuffer b) {
length = b.getInt();
secret = b.getInt();
step = b.getShort();
sid = b.getShort();
payload = new byte[length];
b.get(payload, 0, length);
}
public void print() {
System.out.println(
"length: " + length
+ "\nsecret: " + secret
+ "\n step: " + step
+ "\n sid: " + sid);
bytesToHex(payload);
}
}
}
public static void bytesToHex(byte[] bytes) {
char[] hexArray = "0123456789ABCDEF".toCharArray();
char[] hexChars = new char[bytes.length * 2];
int v;
for ( int j = 0; j < bytes.length; j++ ) {
v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
}
}