Server and client communicating with my own protocol which looks like XMPP. I should to realize chat application. So when one user write String it immedeatly should be sended to other client through the server. I have method sendToAll on server. But user see the message of other user only when it press enter.
How can user receive messages without pressing enter button?
So this is my client:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import org.apache.log4j.Logger;
import dataart.practice.protocols.XMLProtocol;
public class Client {
public static final String SERVER_HOST = "localhost";
public static final Integer SERVER_PORT = 4444;
public static final Logger LOG = Logger.getLogger(Client.class);
private static BufferedReader in;
private static PrintWriter out;
private static BufferedReader inu;
public static void main(String[] args) throws IOException {
System.out.println("Welcome to Client side");
XMLProtocol protocol = new XMLProtocol();
Socket fromserver = null;
fromserver = new Socket(SERVER_HOST, SERVER_PORT);
in = new BufferedReader(new InputStreamReader(fromserver.getInputStream()));
out = new PrintWriter(fromserver.getOutputStream(), true);
inu = new BufferedReader(new InputStreamReader(System.in));
String fuser, fserver;
while (true){
if(in.ready()){//fserver = in.readLine()) != null) {
System.out.println("asdasdsd");
fuser = inu.readLine();
if (fuser != null) {
if (fuser.equalsIgnoreCase("close"))
break;
if (fuser.equalsIgnoreCase("exit"))
break;
protocol.setComId((long) 0);
protocol.setContent(fuser);
protocol.setLogin("Guest");
try {
JAXBContext jaxbContext = JAXBContext.newInstance(XMLProtocol.class);
Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
jaxbMarshaller.setProperty(Marshaller.JAXB_FRAGMENT, false);
jaxbMarshaller.marshal(protocol, out);
out.flush();
} catch (JAXBException e) {
LOG.error("Error while processing protocol" + e);
}
}
}
}
out.close();
in.close();
inu.close();
fromserver.close();
}
}
And Server with ServerThread.
public static void main(String[] args) throws IOException {
LOG.trace("Server started");
ServerSocket s = new ServerSocket(SERVER_PORT);
try {
while (true) {
LOG.trace("Waiting for connections...");
Socket socket = s.accept();
try {
// new ServerThread(socket);
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
userCounter++;
addUser("Guest" + userCounter, out);
LOG.trace("User " + userCounter + " has been added!");
exec.execute(new ServerThread(socket, in, out));
} catch (IOException e) {
socket.close();
}
}
} finally {
s.close();
}
}
ServerThread.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringReader;
import java.net.Socket;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Unmarshaller;
import javax.xml.transform.stream.StreamSource;
import org.apache.log4j.Logger;
import dataart.practice.protocols.XMLProtocol;
import dataart.practice.serverUtils.Commands;
public class ServerThread implements Runnable {
private static final Logger LOG = Logger.getLogger(ServerThread.class);
private XMLProtocol protocol;
private Socket socket;
private BufferedReader in;
private PrintWriter out;
private String buffer = "";// may be exist another. way but it's not working
private Boolean login = false;
public ServerThread(Socket s, BufferedReader in, PrintWriter out) throws IOException {
this.in = in;
this.out = out;
out.println("</XMLProtocol>");
socket = s;
new Thread(this);
}
public void run() {
try {
while (true) {
if ((buffer = in.readLine()) != null) {
if (buffer.endsWith("</XMLProtocol>")) {
protocol = getProtocol(buffer);
//Server.onlineUserList.put(protocol.getLogin(), out);
/* if (!login){
out.println("Maybe login first?");
}
*/
LOG.trace("Getting message from user: " + protocol.getLogin() + " recived message: " + protocol.getContent());
///out.println(protocol.getLogin() + " says:" + protocol.getContent());
Server.sendToAll(protocol.getContent()+"</XMLProtocol>");
} else {
LOG.trace("Nop protocol do not send with it end");
}
}
}
} catch (IOException e) {
LOG.error("Error in reading from stream: " + e);
} catch (JAXBException e) {
LOG.error("Error in Marshalling: " + e);
} finally {
try {
socket.close();
LOG.trace("Socket closed");
} catch (IOException e) {
LOG.error("Socket no closed" + e);
}
}
}
public XMLProtocol getProtocol(String buffer) throws JAXBException {
JAXBContext jaxbContext = JAXBContext.newInstance(XMLProtocol.class);
Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
return (XMLProtocol) jaxbUnmarshaller.unmarshal(new StreamSource(new StringReader(buffer)));
}
public Boolean loginIn(XMLProtocol protocol) {
return true;
}
}
You will need to multi-thread both the client and server. The client will need one thread that listens for messages from the server and writes them to his/her screen and one thread that waits for his/her keyboard input and sends it to the server. Likewise for each connection to the server, it will need a thread waiting for input from the client and one thread sending output from other users to the client.
The reason you don't see incoming messages until you press enter is because of the client while loop. It's commented out now, but it looks like your loop used to:
- Read incoming messages from server
- Read input from keyboard
- Send input to server
So you read whatever was available from the server, and then the client waits for more keyboard input before reading from the server again (in the next iteration).
Another word of advice, from my understanding, creating JAXBContext can be an expensive operation. You don't need to recreate it every time you send a message. Consider initializing one in your server and client and then reusing it for each marshall/unmarshall.
Try this,
Do Not use BufferedReader() with PrintWriter..... PrintWriter is itself the Bridge between byte level socket data and character form.
Eg:
I am showing for a single client, use the while loop for n nos of clients
ServerSocket s = new ServerSocket(4444);
Socket incoming = s.accept();
OutputStream output = s.getOutputStream();
PrintWriter pw = new PrintWriter(output,true);
System.out.println(pw.write(new Scanner(System.in).nextLine()));
Related
I am writing a simple web server program for class that sends files to the web browser on request. I have written as much as I could. The difficulty is getting the data written to the OutputStream. I don't know what I am missing. I couldn't get the simple request to show up on the web browser.
I wrote it to the "name" OutputStream but when I reload the tab in the browser with the URL: "http://localhost:50505/path/file.txt" or any other like that "localhost:50505" it doesn't show up what I wrote to the OutputStream "name". It is supposed to show that.
package lab11;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketImpl;
import java.util.Scanner;
import java.io.OutputStream;
import java.io.PrintWriter;
public class main {
private static final int LISTENING_PORT = 50505;
public static void main(String[] args) {
ServerSocket serverSocket;
try {
serverSocket = new ServerSocket(LISTENING_PORT);
}
catch (Exception e) {
System.out.println("Failed to create listening socket.");
return;
}
System.out.println("Listening on port " + LISTENING_PORT);
try {
while (true) {
Socket connection = serverSocket.accept();
System.out.println("\nConnection from "
+ connection.getRemoteSocketAddress());
handleConnection(connection);
}
}
catch (Exception e) {
System.out.println("Server socket shut down unexpectedly!");
System.out.println("Error: " + e);
System.out.println("Exiting.");
}
}
public static void handleConnection(Socket sok) {
try {
// Scanner in = new Scanner(sok.getInputStream());
InputStream one = sok.getInputStream();
InputStreamReader isr = new InputStreamReader(one);
BufferedReader br = new BufferedReader(isr);
String rootDirectory = "/files";
String pathToFile;
// File file = new File(rootDirectory + pathToFile);
StringBuilder request = new StringBuilder();
String line;
line = br.readLine();
while (!line.isEmpty()) {
request.append(line + "\r\n");
line = br.readLine();
}
// System.out.print(request);
String[] splitline = request.toString().split("\n");
String get = null;
String file = null;
for (String i : splitline) {
if (i.contains("GET")) {
get = i;
String[] splitget = get.split(" ");
file = splitget[1];
}
}
}
OutputStream name = sok.getOutputStream();
Boolean doesexist = thefile.exists();
if (doesexist.equals(true)) {
PrintWriter response = new PrintWriter(System.out);
response.write("HTTP/1.1 200 OK\r\n");
response.write("Connection: close\r\n");
response.write("Content-Length: " + thefile.length() + "\r\n");
response.flush();
response.close();
sendFile(thefile, name);
} else {
System.out.print(thefile.exists() + "\n" + thefile.isDirectory() + "\n" + thefile.canRead());
}
}
catch (Exception e) {
System.out.println("Error while communicating with client: " + e);
}
finally { // make SURE connection is closed before returning!
try {
sok.close();
}
catch (Exception e) {
}
System.out.println("Connection closed.");
}
}
private static void sendFile(File file, OutputStream socketOut) throws
IOException {
InputStream in = new BufferedInputStream(new FileInputStream(file));
OutputStream out = new BufferedOutputStream(socketOut);
while (true) {
int x = in.read(); // read one byte from file
if (x < 0)
break; // end of file reached
out.write(x); // write the byte to the socket
}
out.flush();
}
}
So, I don't know what I really did wrong.
When I load the browser with localhost:50505 it just says can't connect or localhost refused to connect.
You are writing the HTTP response in System.out. You should write it in name, after the headers, in the body of the response. You probably want to describe it with a Content-Type header to make the receiver correctly show the file.
I'm working with "ServerSocket" and "Socket", the problem I'm going through is this: I create a server using serverSocket, I'm waiting for the client to connect, when it connects I'll receive some information, and here's my question, how do I keep listening to the client and receive instructions from it?
In the example below I am creating a server, when the client connects I save the connection within the "clientSocket ".
#GET
#Path("/createServer")
public String conect() throws IOException {
serverSocket = new ServerSocket(3242);
clientSocket = serverSocket.accept();
...
...
}
From this point I need to always listen to this clientSocket, when the client send some information I need to capture to perform some actions, how to do that?
ServerSocket.accept() gives you a java.net.Socket. Doc here
From there on, you can read on that socket using its input stream (Socket.getInputStream()) or write to its output stream (Socket.getOutputStream())
Your sockets (client and server) will live until they're closed, or garbage collected, so remember to keep a strong reference to each one as long as you need them.
Sample programs (simple echo server. Type bye in client to exit):
Server.java
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;
public class Server {
private static volatile boolean stopped = false;
public static void main(String[] args) throws IOException, InterruptedException {
try (ServerSocket server = new ServerSocket(3001)) {
System.out.println("Server ready to accept connections on port " + server.getLocalPort());
final Socket client = server.accept();
System.out.println("Client connected using remote port " + client.getPort());
final Thread t = new Thread(() -> {
try {
try (InputStream clientIn = client.getInputStream()) {
try (OutputStream clientOut = client.getOutputStream()) {
echo(clientIn, clientOut);
}
}
} catch (IOException ioe) {
ioe.printStackTrace();
stopped = true;
}
});
t.setDaemon(true);
t.start();
while (!stopped) {
Thread.sleep(10);
}
System.out.println("Program exit");
}
}
private static void echo(InputStream clientIn, OutputStream clientOut) throws IOException {
try (Scanner clientScan = new Scanner(clientIn, StandardCharsets.UTF_8)) {
try (OutputStreamWriter clientWriter = new OutputStreamWriter(clientOut, StandardCharsets.UTF_8)) {
while (!stopped) {
final String fromClient = clientScan.nextLine();
System.out.println("In: " + fromClient);
clientWriter.write(fromClient);
clientWriter.write(System.lineSeparator());
clientWriter.flush();
if ("bye".equalsIgnoreCase(fromClient.trim())) {
stopped = true;
}
}
System.out.println("Loop done");
}
}
}
}
Client.java
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;
public class Client {
private static volatile boolean stopped = false;
public static void main(String[] args) throws UnknownHostException, IOException {
System.out.println("Client launched");
try (Socket client = new Socket("localhost", 3001)) {
System.out.println("Connected on remote port " + client.getPort() + " from " + client.getLocalPort());
try (Scanner console = new Scanner(System.in)) {
try (OutputStreamWriter toServer = new OutputStreamWriter(client.getOutputStream())) {
final Thread t = new Thread(() -> printEverything(client));
t.setDaemon(true);
t.start();
while (!stopped) {
final String fromConsole = console.nextLine();
if (stopped)
break;
toServer.write(fromConsole);
toServer.write(System.lineSeparator());
toServer.flush();
}
}
}
}
System.out.println("Program exit");
}
private static void printEverything(Socket client) {
try (Scanner server = new Scanner(client.getInputStream())) {
while (!stopped) {
final String fromServer = server.nextLine();
System.out.println("Server said: " + fromServer);
if ("bye".equalsIgnoreCase(fromServer.trim())) {
stopped = true;
}
}
System.out.println("Loop done. Press enter to exit");
} catch (IOException e) {
e.printStackTrace();
stopped = true;
}
}
}
I know this question has been asked before, and I've tried the different solutions, but I got stuck in the implementation part.. :(
Currently multiple clients can connect to the server, I used the multithreaded KnockKnock server/client example from javadocs, and edited it slightly so that you can just send messages to the server, and it will echo them back to you, but I want to be able to make it so that if client 1 sends a message, then the server will broadcast them back to all the clients connected to the server.
I've tried looking around and saw people in the same position as I am in now, and they were told to make a list to keep track of all the connections, and then iterate through the list and send the message, but I really don't know in which class to put it or how to handle it.
If someone could show me or just give me hints to where I should start, it would be greatly appreciated, as I'm really just stuck at the moment :(
Here's where I'm at so far:
Server:
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
public class Server {
public static void main(String[] args) throws IOException {
boolean listening = true;
try (ServerSocket serverSocket = new ServerSocket(4444)) {
while (listening) {
ServerThread thread = new ServerThread(serverSocket.accept());
thread.start();
}
} catch (IOException e) {
System.err.println("Could not listen on port " );
System.exit(-1);
}
}
}
ServerThread
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
public class ServerThread extends Thread{
private Socket socket = null;
public ServerThread(Socket socket) {
super("MultiServerThread");
this.socket = socket;
}
public void run() {
try (
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
socket.getInputStream()));
) {
while (true) {
String input = in.readLine();
System.out.println(input);
out.println("ecco " + input);
if (input.equals("Bye"))
break;
}
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Client (not sure if necessary, but here is it anyways)
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class Client {
public static void main(String[] args) throws IOException {
try (
Socket kkSocket = new Socket("172.30.242.51", 4444);
PrintWriter out = new PrintWriter(kkSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(kkSocket.getInputStream()));
) {
BufferedReader stdIn =
new BufferedReader(new InputStreamReader(System.in));
while (true) {
if(in != null) {
String input = stdIn.readLine();
out.println("Client: " + input);
System.out.println(in.readLine());
out.flush();
}
}
} catch (UnknownHostException e) {
System.err.println("Don't know about host " );
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to " );
System.exit(1);
}
}
}
Have a nice weekend =)
Operation 'write' is blocking in your example. So iterating by all connections can lead to delays and blocking your push thread. Also always set SO_TIMEOUT for socket if you do not want to have memory leaks.
I suggest using netty server
It has very nice functionality for pushing data to all connected clients - look for ChannelGroup
Why don't you use NIO to solve this problem?
A simple example:
public class EchoServer {
public static void main(String[] args) throws Exception {
//Create TCP server channel
ServerSocketChannel serv = ServerSocketChannel.open();
ServerSocket sock = serv.socket();
//Create a socket on your IP and port (i.e: localhost:12345)
SocketAddress addr = new InetSocketAddress(12345);
//Bind server socket and socket address
sock.bind(addr);
//Configure socket so all its methods won't be blocking
serv.configureBlocking(false);
//Create a selector to attend all the incoming requests
Selector selector = Selector.open();
//Register into the selector the accept request type
serv.register(selector,SelectionKey.OP_ACCEPT);
//Create a common buffer
ByteBuffer commonBuffer = ByteBuffer.allocate(10000);
commonBuffer.clear();
Iterator<SelectionKey> it = null;
ByteBuffer channelBuffer = null;
for (;;){ //Infinite loop
System.out.println("Waiting for events......");
selector.select(); // This call do is blocking
System.out.println("New event received");
it = selector.selectedKeys().iterator();
while(it.hasNext()) {
SelectionKey key = (SelectionKey) it.next();
System.out.println(String.format("Processing %s", key));
it.remove(); // Remove it to avoid duplications
try{
if (key.isAcceptable()) {
System.out.println("Received new connection request");
processConnectionRequest(serv, selector);
}else if (key.isReadable()) {
System.out.println("Received new reading request");
processReadingRequest(selector, commonBuffer, key);
}else if (key.isWritable()) {
System.out.println("Received new writing request");
processWritingRequest(key);
}
}catch(Exception e){
key.cancel();
try {
key.channel().close();
} catch (Exception ce) {}
}//end catch
}//end while
}//end for
}//end main
private static void processWritingRequest(SelectionKey key) throws IOException {
SocketChannel cli = (SocketChannel) key.channel();
ByteBuffer buf = (ByteBuffer) key.attachment();
System.out.println(String.format("Wrinting into the channel %s", cli));
buf.flip();//prepare the buffer
buf.rewind();
cli.write(buf);
if (buf.hasRemaining()) {
//If there is more content remaining, compact the buffer
buf.compact();
} else {
buf.clear();
key.interestOps(SelectionKey.OP_READ);
}
}
private static void processReadingRequest(Selector selector, ByteBuffer commonBuffer, SelectionKey key)
throws IOException {
SocketChannel cli = (SocketChannel) key.channel();
if (cli.read(commonBuffer) == -1) {
System.out.println(String.format("Closing channel %s", cli));
cli.close(); // internally calls key.cancel()
}
else {//Send the data to all the channels
commonBuffer.flip();//prepare the buffer
Iterator<SelectionKey> it2 = selector.keys().iterator();
System.out.println("Writing data to all the channels");
SelectionKey keys = null;
while(it2.hasNext()) {
keys = it2.next();
System.out.println(String.format("Writing in %s", keys));
ByteBuffer buf = (ByteBuffer) keys.attachment();
if(buf!=null)
{
buf.put(commonBuffer);
keys.interestOps(SelectionKey.OP_WRITE|SelectionKey.OP_READ);
commonBuffer.rewind();
}
}
commonBuffer.clear();
}
}
private static void processConnectionRequest(ServerSocketChannel serv, Selector selector)
throws IOException, ClosedChannelException {
ByteBuffer channelBuffer;
SocketChannel cli = serv.accept();
cli.configureBlocking(false);
channelBuffer = ByteBuffer.allocate(10000);
System.out.println(String.format("Registering new reading channel: %s", cli));
cli.register(selector, SelectionKey.OP_READ, channelBuffer);
}
}
I've got a client and server coded in Java, once the server has received one message from the client, the server stops receiving all new messages. No errors are thrown when the client tries to sent more messages. I can't seem to find out why it doesn't allow or receive new connections! Please help.
public class Server implements Runnable {
#Override
public void run() {
ServerSocket echoServer = null;
String line;
DataInputStream is;
PrintStream os;
Socket clientSocket = null;
boolean Listening = true;
int sPort = 9999;
// Try to open a server socket on port 9999
try {
echoServer = new ServerSocket(sPort);
}
catch (IOException e) {
System.out.println(e);
}
// Create a socket object from the ServerSocket to listen and accept
// connections.
// Open input and output streams
while (Listening){
try {
clientSocket = echoServer.accept();
is = new DataInputStream(clientSocket.getInputStream());
//os = new PrintStream(clientSocket.getOutputStream());
// As long as we receive data, echo that data back to the client.
while (true) {
line = is.readLine();
if(line != null){
//os.println(line);
log(Level.SEVERE, "New connection to server {0}", line);
}
}
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
while (true)
{
line = is.readLine();
if(line != null){
//os.println(line);
log(Level.SEVERE, "New connection to server {0}", line);
}
}
after accepting a connection it is entering into this infinite loop.due to this loop it will never accept new connection.
to solve this issues, start new thread each time when new client comes, pass socket connection of the client and read data from that client.
I see two issues as below:
while (true) {
line = is.readLine();
if(line != null){
//os.println(line);
log(Level.SEVERE, "New connection to server {0}", line);
}
Here you need to break after reading the content from the Socket irrespective of whether you read in different thread or same.
You need to declare boolean Listening to volatile else the server wont stop.
while (true) {
line = is.readLine();
if(line != null){
//os.println(line);
log(Level.SEVERE, "New connection to server {0}", line);
}
}
the code will block new request, so the second request will not be accepted.
I make an example accounding to your code. Hope it help to you.
The Server Class will only be userd to accept socket connection and create a new thread to process it.
import java.io.DataInputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.io.Writer;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Server implements Runnable {
#Override
public void run() {
ServerSocket echoServer = null;
boolean listening = true;
Socket clientSocket = null;
int sPort = 9999;
// Try to open a server socket on port 9999
try {
echoServer = new ServerSocket(sPort);
} catch (IOException e) {
System.out.println(e);
}
// Create a socket object from the ServerSocket to listen and accept
// connections.
// Open input and output streams
while (listening) {
try {
clientSocket = echoServer.accept();
System.out.println("receive new connection");
new ProcessClientThread(clientSocket).start();
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE,
null, ex);
}
}
}
}
The ProcessClientThread Class extends Thread Class and defined a constructor with a Socket type parameter. Override run method of it. The run method get input stream from socket and print it out. When it accept 0, it will close the scoket connection. Its code like this
import java.io.DataInputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.net.Socket;
public class ProcessClientThread extends Thread {
Socket socket = null;
public ProcessClientThread(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
DataInputStream is;
String line;
boolean flag = true;
try {
is = new DataInputStream(socket.getInputStream());
while (flag) {
line = is.readLine();
if (Integer.valueOf(line) != 0) {
// os.println(line);
// Logger.getLogger(Level.SEVERE,
// "New connection to server {0}", line);
System.out.println(line);
} else {
Writer w = new OutputStreamWriter(socket.getOutputStream());
w.write(0);
w.flush();
flag = false;
socket.close();
System.out.println("close a connection");
}
}
} catch(Exception e) {
}
}
}
There is a StartUp Class which used to start up the server thread.
public class StartUp {
public static void main(String[] args) {
new Thread(new Server()).start();
}
}
Run the below Client Class to test the Server.
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.net.Socket;
public class Client {
public static void main(String[] args) throws Exception {
Socket client = new Socket("localhost", 9999);
OutputStreamWriter writer = new OutputStreamWriter(client.getOutputStream());
Reader reader = new InputStreamReader(System.in);
Reader serverReader = new InputStreamReader(client.getInputStream());
boolean flag = true;
while(flag) {
int readContent = reader.read();
writer.write(readContent);
writer.flush();
if(readContent == 0) {
writer.close();
client.close();
flag = false;
}
}
}
}
I am trying to launch server and client thread on the same process, but seems like the server thread is blocking the client thread (or vice versa). I'm not allowed to use any global variable between those threads(like semaphore or mutex, since the client and the server thread are launched by upper-class that I don't have the access of).
I found a similar question here , but it still use two different process (two main function).
Here is a sample of my code
The server code:
public class MyServer implements Runnable{
ServerSocket server;
Socket client;
PrintWriter out;
BufferedReader in;
public MyServer() throws IOException{
server = new ServerSocket(15243, 0, InetAddress.getByName("localhost"));
}
#Override
public void run() {
while(true){
try {
ArrayList<String> toSend = new ArrayList<String>();
System.out.println("I'll wait for the client");
client = server.accept();
out = new PrintWriter(client.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
String inputLine;
while((inputLine = in.readLine()) != null){
toSend.add("answering : "+inputLine);
}
for(String resp : toSend){
out.println(resp);
}
client.close();
out.close();
in.close();
} catch (IOException ex) {
}
}
}
}
And the client code:
public class MyClient implements Runnable{
Socket socket;
PrintWriter out;
BufferedReader in;
public MyClient(){
}
#Override
public void run() {
int nbrTry = 0;
while(true){
try {
System.out.println("try number "+nbrTry);
socket = new Socket(InetAddress.getByName("localhost"), 15243);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out.println("Hello "+nbrTry+" !! ");
String inputLine;
while((inputLine = in.readLine()) != null){
System.out.println(inputLine);
}
nbrTry++;
} catch (UnknownHostException ex) {
} catch (IOException ex) {
}
}
}
}
And the supposed upper-class launching those thread:
public class TestIt {
public static void main(String[] argv) throws IOException{
MyServer server = new MyServer();
MyClient client = new MyClient();
(new Thread(server)).start();
(new Thread(client)).start();
}
}
It gives me as output:
I'll wait for the client
Try number 0
And it stuck here. What should I do to keep both server and client code running?
Thank you.
I'll be willing to take up your questions but basically you need to think through your logic a bit more carefully.
MyServer.java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
public class MyServer implements Runnable {
ServerSocket server;
public MyServer() throws IOException {
server = new ServerSocket(15243, 0, InetAddress.getByName("localhost"));
}
#Override
public void run() {
while (true) {
try {
// Get a client.
Socket client = server.accept();
// Write to client to tell him you are waiting.
PrintWriter out = new PrintWriter(client.getOutputStream(), true);
out.println("[Server] I'll wait for the client");
// Let user know something is happening.
System.out.println("[Server] I'll wait for the client");
// Read from client.
BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
String inputLine = in.readLine();
// Write answer back to client.
out.println("[Server] Answering : " + inputLine);
// Let user know what it sent to client.
System.out.println("[Server] Answering : " + inputLine);
in.close();
out.close();
client.close();
} catch (Exception e) {
}
}
}
}
MyClient.java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class MyClient implements Runnable {
Socket socket;
PrintWriter out;
BufferedReader in;
public MyClient() throws UnknownHostException, IOException {
}
#Override
public void run() {
int nbrTry = 0;
while (true) {
try {
// Get a socket
socket = new Socket(InetAddress.getByName("localhost"), 15243);
// Wait till you can read from socket.
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String inputLine = in.readLine();
//inputLine contains the text '[Server] I'll wait for the client'. means that server is waiting for us and we should respond.
// Write to socket
out = new PrintWriter(socket.getOutputStream(), true);
out.println("[Client] Hello " + nbrTry + " !! ");
// Let user know you wrote to socket
System.out.println("[Client] Hello " + nbrTry++ + " !! ");
} catch (UnknownHostException ex) {
} catch (IOException ex) {
}
}
}
}
TestIt.java
import java.io.IOException;
public class TestIt {
public static void main(String[] argv) throws IOException {
MyServer server = new MyServer();
MyClient client = new MyClient();
(new Thread(server)).start();
(new Thread(client)).start();
}
}
Your client sends a string, then reads until the stream is exhausted:
while((inputLine = in.readLine()) != null){
BufferedReader.readLine() only returns null at the end of the stream, as I recall. On a stream, it will block until input is available
Your server receives until the stream is exhausted, then sends back its response.
After sending one line, you now have:
Your client waiting for a response.
Your server still waiting for more data from the client. But it doesn't send anything back until the end of the stream from the client (which never happens because the client is waiting for your response).