Develop Reference

how can send http request and get its information in Java?

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class TCPClient2 {
public static void main(String[] args) throws IOException {
if (args.length != 2) {
System.out.println("Incorrect number of args, exiting...");
System.exit(0);
}
String host_address = args[0];
String resource = args[1];
Socket socket =null;
PrintWriter out = null;
BufferedReader in = null;
int port=80;
try {
socket = new Socket(host_address,port);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
}
catch (UnknownHostException e) {
System.out.println("Unknown host");
System.exit(-1);
}
catch (IOException e) {
System.out.println("No I/O");
System.exit(-1);
}
try {
String request_line = "GET " + resource + " HTTP/1.1";
String host_header = "Host: " + host_address;
out.println(request_line);
out.println(host_header);
out.println(); // blank line = end of request header
String line;
while((line = in.readLine()) != null)
{
System.out.println(line);
}
}
catch (IOException e) {
System.out.println("Error during communication");
System.exit(-1);
}try {
socket.close();
}
catch (IOException e) {
System.out.println("Cannot close the socket");
System.exit(-1);
}
}
}
hello ,i have just started learning java network programming, i tried to send a http request and i was expecting getting its information but it returns "No I/O" all the time but it connects to server . Can any one tell where do i make mistake ?

My chat server is responding to the correct thread/client but send button must be clicked equal to the number of clients

I have made a chat server using socket that can handle multiple clients and can reply to individual clients..the client can chat only with the server..But as the number client increases, the server has to click send button as same as the client's number.....i.e; one click to reply when there is only one client connected...click twice when there is two clients and so on..... how can i solve it???
The server is like:
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.PrintStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.ServerSocket;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Stream;
import javax.swing.SwingUtilities;
public class NewClass1{
private static ServerSocket serverSocket = null;
static Socket clientSocket = null;
private static final int maxClientsCount = 10;
private static final clientThread[] threads = new clientThread[maxClientsCount];
private static LinkedHashMap<String, clientThread> hm = new LinkedHashMap<String, clientThread>();
public static HashMap<String, clientThread> getinfo(){
return hm;
}
public static void main(String args[]) {
int portNumber = 22222;
if (args.length < 1) {
System.out.println("Usage: java MultiThreadChatServerSync <portNumber>\n"
+ "Now using port number=" + portNumber);
} else {
portNumber = Integer.valueOf(args[0]).intValue();
}
try {
serverSocket = new ServerSocket(portNumber);
} catch (IOException e) {
System.out.println(e);
}
while (true) {
try {
clientSocket = serverSocket.accept();
int i = 0;
for (i = 0; i < maxClientsCount; i++) {
if (threads[i] == null) {
(threads[i] = new clientThread(clientSocket, threads)).start();
System.out.println("hiiiiiiiiiii");
break;
}
}
if (i == maxClientsCount) {
PrintStream os = new PrintStream(clientSocket.getOutputStream());
os.println("Server too busy. Try later.");
os.close();
clientSocket.close();
}
} catch (IOException e) {
System.out.println(e);
}
}
}
}
class clientThread extends Thread {
static String clientName = null;
private BufferedReader br=null;
private DataInputStream is = null;
private PrintStream os = null;
private static Socket clientSocket = null;
private final clientThread[] threads;
private int maxClientsCount;
private static HashMap<String, clientThread> hm = new HashMap<>();
public clientThread(Socket clientSocket, clientThread[] threads) {
this.clientSocket = clientSocket;
this.threads = threads;
maxClientsCount = threads.length;
this.hm=NewClass1.getinfo();
}
public void run() {
final int maxClientsCount = this.maxClientsCount;
final clientThread[] threads = this.threads;
try {
br= new BufferedReader(new InputStreamReader(System.in));
is = new DataInputStream(clientSocket.getInputStream());
os = new PrintStream(clientSocket.getOutputStream());
os.flush();
String name;
while (true) {
os.println("Enter your name.");
name = is.readLine().trim();
if (name.indexOf('#') == -1) {
break;
} else {
os.println("The name should not contain '#' character.");
}
}
System.out.println("\n"+name+" has joined");
os.println("Welcome " + name
+ " to our chat room.\nTo leave enter /quit in a new line.");
synchronized (this) {
for (int i = 0; i < maxClientsCount; i++) {
if (threads[i] != null && threads[i] == this) {
clientName = "#"+name;
hm.put(clientName, this);
break;
}
}
for (int i = 0; i < maxClientsCount; i++) {
if (threads[i] != null && threads[i] != this) {
threads[i].os.println("*** A new user " + clientName
+ " entered the chat room !!! ***");
}
}
}
new Thread(new New()).start();
while(true){
String line=br.readLine();
if (line.startsWith("#")) {
String[] words = line.split("\\s", 2);
if (words.length > 1 && words[1] != null) {
words[1] = words[1].trim();
if (!words[1].isEmpty()) {
for(Map.Entry<String,clientThread> e:hm.entrySet()){
if(words[0].equals(e.getKey())){
clientThread get=e.getValue();
get.os.println("Server:\t" + words[1]);
os.flush();
System.out.println("\nServer to "+e.getKey()+":\t"+words[1]);
break;
}
else{
continue;
}
}
}}}
else { System.out.println("Please type #recipent's name.");
}}
} catch (IOException e) {
}
}
}
class New extends Thread{
public void run(){
DataInputStream is = null;
try {
is = new DataInputStream(NewClass1.clientSocket.getInputStream());
String lin=null;
while((lin=is.readLine())!=null)
{
//lin=is.readLine();
System.out.println(clientThread.clientName+": "+lin);
}
} catch (IOException ex) {
Logger.getLogger(New.class.getName()).log(Level.SEVERE, null, ex);
} finally {
try {
is.close();
} catch (IOException ex) {
Logger.getLogger(New.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
The client is like:
import java.io.DataInputStream;
import java.io.PrintStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
public class NewClass implements Runnable {
// The client socket
private static Socket clientSocket = null;
// The output stream
private static PrintStream os = null;
// The input stream
private static DataInputStream is = null;
private static BufferedReader inputLine = null;
private static boolean closed = false;
public static void main(String[] args) {
// The default port.
int portNumber = 22222;
// The default host.
String host = "localhost";
if (args.length < 2) {
System.out
.println("Usage: java MultiThreadChatClient <host> <portNumber>\n"
+ "Now using host=" + host + ", portNumber=" + portNumber);
} else {
host = args[0];
portNumber = Integer.valueOf(args[1]).intValue();
}
/*
* Open a socket on a given host and port. Open input and output streams.
*/
try {
clientSocket = new Socket(host, portNumber);
inputLine = new BufferedReader(new InputStreamReader(System.in));
os = new PrintStream(clientSocket.getOutputStream());
is = new DataInputStream(clientSocket.getInputStream());
} catch (UnknownHostException e) {
System.err.println("Don't know about host " + host);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to the host "
+ host);
}
/*
* If everything has been initialized then we want to write some data to the
* socket we have opened a connection to on the port portNumber.
*/
if (clientSocket != null && os != null && is != null) {
try {
/* Create a thread to read from the server. */
new Thread(new NewClass()).start();
while (!closed) {
String msg=inputLine.readLine();
os.println(msg.trim());
os.flush();
System.out.println("\nClient: \t"+msg);
}
/*
* Close the output stream, close the input stream, close the socket.
*/
os.close();
is.close();
clientSocket.close();
} catch (IOException e) {
System.err.println("IOException: " + e);
}
}
}
/*
* Create a thread to read from the server. (non-Javadoc)
*
* #see java.lang.Runnable#run()
*/
public void run() {
/*
* Keep on reading from the socket till we receive "Bye" from the
* server. Once we received that then we want to break.
*/
String responseLine;
try {
while ((responseLine = is.readLine()) != null) {
System.out.println("\n"+responseLine);
if (responseLine.indexOf("*** Bye") != -1)
break;
}
closed = true;
} catch (IOException e) {
System.err.println("IOException: " + e);
}
}
}

transformer to socket not working

Its driving me nuts trying days to grind this problem.
I am writing a java server to work with an android application. They communicate text string and xml.
Currently simple socket communication seems fine, however it breaks down when I tried to use transformer instead of simple println.
Server code as below
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.Charset;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
public class javamultithreadedserver implements Runnable {
Socket csocket;
static int listenport = 6021;
public static final String endOfCom = "endofcom";
String connectionname;
public javamultithreadedserver(Socket csocket, String connectionname) {
this.csocket = csocket;
this.connectionname = connectionname;
}
public static void main(String[] args) throws Exception {
int listentoport = 0;
//System.out.println(args.length);
if (args.length == 1){
listentoport = Integer.parseInt(args[0]);
} else{
listentoport = listenport;
}
ServerSocket ssock = new ServerSocket(listentoport);
System.out.println("Listening at port " + listentoport);
while (true) {
Socket sock = ssock.accept();
System.out.println("Connected. from: " + sock.getInetAddress().getHostAddress() + " " + sock.getInetAddress().getHostName() + " port: " + sock.getPort() + " " + sock.getInetAddress().getCanonicalHostName());
new Thread(new javamultithreadedserver(sock, sock.getInetAddress().getHostAddress() + " " + sock.getInetAddress().getHostName() + " " + sock.getInetAddress().getCanonicalHostName())).start();
}
}
#Override
public void run() {
try {
PrintWriter out = new PrintWriter(csocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(csocket.getInputStream()));
PrintStream pstream = new PrintStream (csocket.getOutputStream(), true);
String inputLine, outputLine;
System.out.println(connectionname + ": listening for query information.");
while ((inputLine = in.readLine()) != null) {
System.out.println(connectionname + ": " + inputLine);
//out.write("received something");
DBQuery q = new DBQuery(inputLine + DBQuery.regexsplit + "connectionname" + DBQuery.regexsplit + connectionname);
DOMSource dmsource = q.returns();
***//StreamResult consoleResult = new StreamResult(System.out); //debug***
StreamResult consoleResult = new StreamResult(pstream);
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
Thread.sleep(100);
***transformer.transform(dmsource, consoleResult);***
//out.println("println this is a testprogram"); // client receive ok
pstream.flush();
System.out.println(connectionname + ": reply sent.");
if (inputLine == endOfCom){
System.out.println(connectionname + ": is satisfied and terminated communication.");
break;
}
}
pstream.close();
csocket.close();
}catch (IOException e) {
System.out.println(e);
}catch (Exception e) {
System.out.println(e);
}
}
}
And the android client code as below:
public void run() {
if (barcode.length() > 0) {
Socket socket = null;
try {
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
socket = new Socket(serverAddr, SERVERPORT);
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
socket.setSoTimeout(10000);
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out.write(barcode + ENDL);
if(out.checkError()){
showToUI("PrintWriter had error");
} else {
showToUI("Query sent");
}
int i = 0;
while (true) {
try{
if (**(serverResponse = in.readLine()) != null**) {
if(serverResponse == endOfCom){
Log.i("communicated all data", "bye");
out.write(endOfCom + ENDL);
break;
} else{
}
Log.i("server says", serverResponse);
}
//Log.i("server says", (serverResponse == null? "null" :serverResponse ));
}catch(SocketTimeoutException e){
showToUI(barcode + ": Server did not respond in time");
if (i++ > 2) {
break;
}
}
}
} catch (final UnknownHostException e1) {
showToUI(e1.toString());
} catch (final IOException e1) {
showToUI(e1.toString());
} finally{
try {
socket.close();
} catch (IOException e) {
showToUI(e.toString());
}
}
}else{
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "Please enter something in barcode", Toast.LENGTH_SHORT).show();
}
});
}
}
I have tested that the xml result returned was ok, if the Stream Result was set to System.out instead of the PrintStream pstream, everything prints perfectly to the console.
However with or without pstream.flush(), client received no response at (serverResponse = in.readLine()) != null.
Also the PrintWriter out which was based on the same Socket socket of pstream successfully gave feedback to the client. When out.println("println this is a testprogram"); was called, the client received log at the Log.i("server says", serverResponse); line OK.
One thing to note is that the reply is usually quite long, can be up to 65536 characters or even more, I do not know if that has any implication, I have tried to create a Buffered reader on the android app larger than the replying xml, it still did not work. The machines are communicating on local network, java server program is running on a different machine from the android emulator.
Any help is appreciated, this had been going on for days and nowhere.

readLine() won't return null until the peer closes the connection. And when it does return null, you need to break out of the loop. And don't compare string s with ==.

Java: Client-Server, chat broadcasting

I"m working on a Client-Server chat program for a university project and I have little programming background. I've made 3 classes: ChatClient, ChatServer and ChatServerThread. I can currently have multiple clients connected and talking to the server at any time.
Although one of the requirements that I'm having the most difficulty is this: "Any message typed from 1 client is sent to all other clients" and also "Both sent and received messages should be displayed".
I've spent the last few nights just trying to get this extra bit of functionality working but have had no luck.
I've been reading and looking around for a while but I have lots of difficulty adapting online examples to my work. I've read that I should be creating a list of sockets and then iterate through the list and send data to everyone in the list, which makes sense in my head but gives me a headache when I try implementing it. Any help with this would be very greatly appreciated. Extra points if anyone can give me some insight on how I could encrypt the sent data.
ChatClient
import java.net.*;
import java.io.*;
public class ChatClient {
private Socket socket = null;
private DataInputStream console = null;
private DataOutputStream streamOut = null;
private String myName = null;
private BufferedReader StreamIn = null;
private String response = null;
public ChatClient(String serverName, int serverPort) {
try {
console = new DataInputStream(System.in);
System.out.println("What is your name?");
myName = console.readLine();
System.out.println(myName + " <" + InetAddress.getLocalHost() + "> ");
} catch (IOException ioe) {
System.out.println("Unexpected exception: " + ioe.getMessage());
}
System.out.println("Establishing connection. Please wait ...");
try {
socket = new Socket(serverName, serverPort);
System.out.println("Connected: " + socket);
StreamIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
streamOut = new DataOutputStream(socket.getOutputStream());
streamOut.writeUTF(":" + myName + " <" + InetAddress.getLocalHost() + "> HAS JOINED");
streamOut.flush();
} catch (UnknownHostException uhe) {
System.out.println("Host unknown: " + uhe.getMessage());
} catch (IOException ioe) {
System.out.println("Unexpected exception: " + ioe.getMessage());
}
String line = "";
while (!line.equals(".bye")) {
try {
line = console.readLine();
streamOut.writeUTF(myName + " <" + InetAddress.getLocalHost() + "> : " + line);
streamOut.flush();
} catch (IOException ioe) {
System.out.println("Sending error: " + ioe.getMessage());
}
}
}
public void stop() {
try {
if (console != null) console.close();
if (streamOut != null) streamOut.close();
if (socket != null) socket.close();
} catch (IOException ioe) {
System.out.println("Error closing ...");
}
}
public static void main(String args[]) {
ChatClient client = null;
if (args.length != 2)
System.out.println("Usage: java ChatClient host port");
else
client = new ChatClient(args[0], Integer.parseInt(args[1]));
}
}
ChatServer
import java.net.*;
import java.io.*;
import java.util.*;
public class ChatServer implements Runnable {
private ServerSocket server = null;
private Thread thread = null;
private ChatServerThread client = null;
private String clientSentence = null;
private int peers = 0;
private List clients = new ArrayList();
final List sockets = new ArrayList();
public ChatServer(int port) {
try {
System.out.println("Binding to port " + port + ", please wait ...");
server = new ServerSocket(port);
System.out.println("Server started: " + server);
start();
} catch (IOException ioe) {
System.out.println(ioe);
}
}
public void run() {
while (thread != null) {
try {
System.out.println("Waiting for a client ...");
addThread(server.accept());
} catch (IOException ie) {
System.out.println("Acceptance Error: " + ie);
}
}
}
public void addThread(Socket socket) {
System.out.println("Client accepted: " + socket);
client = new ChatServerThread(this, socket);
try {
client.open();
client.start();
} catch (IOException ioe) {
System.out.println("Error opening thread: " + ioe);
}
}
public void start() {
if (thread == null) {
thread = new Thread(this);
thread.start();
}
}
public void stop() {
if (thread != null) {
thread.stop();
thread = null;
}
}
public void increment(String sentence) {
peers++;
String[] info = sentence.split(" ");
String name = info[0].replace(":", "");
System.out.println(name + " Has joined the room, we now have " + peers + " peer(s).");
clients.add(name);
}
public Boolean isAllowed(String name, Socket socket) {
try {
String stringSearch = name;
BufferedReader bf = new BufferedReader(new FileReader("allowed.txt"));
int linecount = 0;
String line = "";
System.out.println("Searching for " + stringSearch + " in file...");
while ((line = bf.readLine()) != null) {
linecount++;
String[] words = line.split(" ");
for (String word : words) {
if (word.equals(stringSearch)) {
System.out.println("User is allowed");
registerSocket(socket);
return true;
}
}
}
bf.close();
} catch (IOException e) {
System.out.println("IO Error Occurred: " + e.toString());
}
System.out.println("User is not allowed");
return false;
}
public void showAll() {
for (int i = 0; i < clients.size(); i++) {
System.out.print(clients.get(i));
}
}
public void registerSocket(Socket socket) {
//socket = new DataOutputStream(socket.getOutputStream());
sockets.add(socket);
for (int i = 0; i < sockets.size(); i++) {
System.out.println(sockets.get(i));
}
}
public static void main(String args[]) {
ChatServer server = null;
if (args.length != 1)
System.out.println("Usage: java ChatServer port");
else
server = new ChatServer(Integer.parseInt(args[0]));
}
}
ChatServerThread
import java.net.*;
import java.io.*;
public class ChatServerThread extends Thread {
private Socket socket = null;
private ChatServer server = null;
private int ID = -1;
private DataInputStream streamIn = null;
private String clientSentence = null;
public String newGuy = null;
DataOutputStream streamOut = null;
public ChatServerThread(ChatServer _server, Socket _socket) {
server = _server;
socket = _socket;
ID = socket.getPort();
}
public void run() {
System.out.println("Server Thread " + ID + " running.");
while (true) {
try {
String sentence = streamIn.readUTF();
//System.out.println(sentence);
char c = sentence.charAt(0);
String[] command = null;
command = sentence.split(" ");
String name = command[0].substring(1);
System.out.println("Sending out: " + sentence + " via ");
streamOut.writeBytes(sentence);
if (c == ':') {
if (server.isAllowed(name, socket))
server.increment(sentence);
else {
close();
}
}
} catch (IOException ioe) {
}
}
}
public void open() throws IOException {
streamIn = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
}
public void close() throws IOException {
if (socket != null) socket.close();
if (streamIn != null) streamIn.close();
}
}

Why is this basic client-server program not passing data?

I am following the Java Trail on networking. The three KnockKnock classes used as examples (client, server, and protocol) work as intended when I copy/paste them into Eclipse. However, what I really want to do is eliminate the protocol class and just have the server echo back to the client whatever I type into the console. I tried modifying the server program mainly by commenting out references to the protocol class, but somehow, I ended up breaking the program.
I am so new that I am clueless as to what is wrong and the more I search for an answer in ebooks and on websites the more confused I get. All I have discovered is that I know next to nothing about how IO streams really work. I pasted all three classes below in the order: server, client, protocol. Where is the problem and why is it a problem:
Server:
import java.net.*;
import java.io.*;
public class KnockKnockServer {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
System.out.println("Client Accepted");
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
String inputLine, outputLine;
//KnockKnockProtocol kkp = new KnockKnockProtocol();
//outputLine = kkp.processInput(null);
//out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
//outputLine = kkp.processInput(inputLine);
//out.println(outputLine);
out.println(inputLine);
if (inputLine.equals("Bye."))
break;
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
}
Client:
import java.io.*;
import java.net.*;
public class KnockKnockClient {
public static void main(String[] args) throws IOException {
Socket kkSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
kkSocket = new Socket("localhost", 4444);
out = new PrintWriter(kkSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: taranis.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: taranis.");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer;
String fromUser;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
out.close();
in.close();
stdIn.close();
kkSocket.close();
}
}
Protocol:
import java.net.*;
import java.io.*;
public class KnockKnockProtocol {
private static final int WAITING = 0;
private static final int SENTKNOCKKNOCK = 1;
private static final int SENTCLUE = 2;
private static final int ANOTHER = 3;
private static final int NUMJOKES = 5;
private int state = WAITING;
private int currentJoke = 0;
private String[] clues = { "Turnip", "Little Old Lady", "Atch", "Who", "Who" };
private String[] answers = { "Turnip the heat, it's cold in here!",
"I didn't know you could yodel!",
"Bless you!",
"Is there an owl in here?",
"Is there an echo in here?" };
public String processInput(String theInput) {
String theOutput = null;
if (state == WAITING) {
theOutput = "Knock! Knock!";
state = SENTKNOCKKNOCK;
} else if (state == SENTKNOCKKNOCK) {
if (theInput.equalsIgnoreCase("Who's there?")) {
theOutput = clues[currentJoke];
state = SENTCLUE;
} else {
theOutput = "You're supposed to say \"Who's there?\"! " +
"Try again. Knock! Knock!";
}
} else if (state == SENTCLUE) {
if (theInput.equalsIgnoreCase(clues[currentJoke] + " who?")) {
theOutput = answers[currentJoke] + " Want another? (y/n)";
state = ANOTHER;
} else {
theOutput = "You're supposed to say \"" +
clues[currentJoke] +
" who?\"" +
"! Try again. Knock! Knock!";
state = SENTKNOCKKNOCK;
}
} else if (state == ANOTHER) {
if (theInput.equalsIgnoreCase("y")) {
theOutput = "Knock! Knock!";
if (currentJoke == (NUMJOKES - 1))
currentJoke = 0;
else
currentJoke++;
state = SENTKNOCKKNOCK;
} else {
theOutput = "Bye.";
state = WAITING;
}
}
return theOutput;
}
}

I think your problem is just both apps are waiting:
when KKServer starts, it waits for a client, and then it's waiting until the client "says" something, and the client is waiting until the server says something before waiting for the user input