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Socket Programming - Java - Not receiving some messages

I just started working on Sockets with both client and server threads in the same Node. Below is my code structure -
I have a Node class which makes connections to different Nodes. It sends REQUEST messages to the Nodes and waits till it gets REPLY from all the nodes tracked using the outstandingreplies variable which is static and volatile, also has synchronised getters and setters.
Server Class spawns Processor thread which processes each message that it hears.
It modifies certain variables which furthers the code execution. On getting a REPLY message, it decrements outstandingreplies variable. It also sends messages to node which just sent the messages based on certain conditions.
Below is my code, I have removed certain details.
Node Class
// Creates connections to other Nodes(machines) and sends messages
public class Node {
public static volatile int timestamp = 0;
public static volatile int highestTimestamp = 0;
public static int csCounter = 0;
public static int nodeId;
public static int n;
public static String[] hosts;
public static int[] ports;
public static volatile int[] deferredNodes;
public static volatile boolean requestingCS = false;
public static volatile int outstandingReplies;
// skipping getters and setters for variables shared between server and client threads
// method to connect the node with other nodes
public static Connection connect() {
// skipping standar code to create sockets
}
public static void main(String[] args) {
// start the receiver
Server server = new Server();
server.start();
// make the connections with other nodes
Connection connections = connect();
while (counter <= 2) {
// create a message
Message message = new Message(); // skipping details to create a msg
// send requests to all other nodes
for (int i = 0; i < n; i++) {
if (i != nodeId) {
System.out.println("Sending message " + message + " to node " + i);
try {
connections.outs[i].writeObject(message);
outstandingReplies++;
} catch (Exception e) {
e.printStackTrace();
}
}
}
// All REQUEST messages sent, WAIT for all replies
while (outstandingReplies != 0) {
// System.out.println("Waiting for replies");
}
// send REPLY msg based on some logic
if(logic is true){
// send messages to other nodes
Message replyMessage = new Message("REPLY", timestamp, nodeId);
try {
connections.outs[i].writeObject(replyMessage);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Connections Class
// Stores all the connections created by the Node Class
Server Class
// Listens to requests from nodesand spawns a Processor thread for each socket
public class Server extends Thread {
#Override
public void run() {
try {
System.out.println("Starting the node's receiver thread");
// create a serversocket to listen to requests
ServerSocket serverSocket = new ServerSocket(Node.ports[Node.nodeId]);
for (int i = 0; i < Node.n - 1; i++) {
System.out.println("Opening sockets");
Socket socket = serverSocket.accept();
// create a processor thread for each to read and process the incoming Messages
Processor processor = new Processor(socket);
System.out.println("Starting message processor");
processor.start();
}
} catch (IOException e) {
e.printStackTrace();
}
}
Processor Class
// Processes the messages and sends reply when needed
public class Processor extends Thread {
Socket socket;
int[] replies = new int[10];
public Processor(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
try {
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
ObjectOutputStream out = new ObjectOutputStream(
socket.getOutputStream());
while (true) {
System.out.println("Waiting for msg");
System.out.println("Socket is " + socket.isConnected());
Message message = (Message) in.readObject();
Node.timestamp = Math.max(Node.timestamp + 1, message.timestamp);
// printing the queue here
System.out.println("Processor received " + message);
// if message is a request
if (message.type.trim().equals("REQUEST")) {
if(condition is true){
// do something
} else {
// send reply to node who sent you message
Message replyMessage = new Message("REPLY", Node.timestamp,
Node.nodeId);
System.out.println(
"Send " + replyMessage + " to " + Node.hosts[message.nodeId]);
out.writeObject(replyMessage);
}
}
if (message.type.trim().equals("REPLY")) {
// do something
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
I run this code on two machines. The connections are established successfully and some messages are exchanged. However, in some cases the Processor class does not get message even when the socket is still connected.
I did go through some questions on missing messages with Java sockets which mentioned that when nodes gets two messages at once, it processes only the first message and the second message is buffered. I am not sure how I can check if that is the case with my code.
I am guessing something is wrong with I am handling sockets. Would really help if anyone could point where I am doing things incorrectly.
TIA

simple multi-threaded server chat using java

I'm creating a java chat server that handles multi clients I use this simple code for server
public class Server extends Thread {
ServerSocket serverSocket = null;
Socket socket = null;
private int unique_id;
ArrayList<Clients> cl;
public Server(int port) {
try {
serverSocket = new ServerSocket(port);
cl = new ArrayList<>();
this.start();
} catch (Exception e){
System.out.println("Error 5");
e.printStackTrace();
}
}
#Override
public void run(){
System.out.println("Server Start");
while (true){
try {
socket = serverSocket.accept();
Clients t = new Clients(socket); // add it to thread
cl.add(t);
t.start();
System.out.println("Connected " + String.valueOf(cl.size())); // printed ok
}catch (Exception e){
System.out.println("Error 4");
e.printStackTrace();
}
}
}
public synchronized void SendToAll(String s){ // this function used by client when one of client socket send a message then server send it to all
System.out.println("Sended is excuted"); // excuted normal each time i send a message from client but not send to all
for (int i = 0; i < cl.size(); i++){
cl.get(i).WriteToSocket(s);
}
}
public static void main(String args[]){
int port = 5002;
Server server = new Server(port); // start server
//server.run(); // start connections wait for it
}
class Clients extends Thread { // class extends thread
public Socket socket = null;
DataInputStream input = null; // read input
DataOutputStream output = null; // read output
public int myid = 0; // unique id for each client
public Clients(Socket soc) {
socket = soc;
try {
input = new DataInputStream(socket.getInputStream());
output = new DataOutputStream(socket.getOutputStream());
myid = ++unique_id;
System.out.println("Client Start Thread"); // printed ok !
} catch (IOException e){
System.out.println("Error 1");
e.printStackTrace();
}
}
public void WriteToSocket(String s) { // used to write a message to this socket
try {
output.write(s.getBytes());
}catch (IOException e){
System.out.println("Error 2");
e.printStackTrace();
}
}
#Override
public void run() { // run thread function wait for messages from clients
while (true){
try {
String s = input.readLine();
if (s.contains("quite")) {
socket.close();
input.close();
output.close();
cl.remove(this);
this.stop();
}
if (!s.isEmpty()) {
SendToAll(s);// when message come and not empty it use server function to send them to all clients
}
}catch (IOException e){
System.out.println("Error 3");
e.printStackTrace();
}
}
}
}
}
everything works fine when clients connect the server accept the connection and the client thread started
but the problem when I sent a message from the client it didn't received by the server I try my client application in java too with Qt c++ server and it works ?
so what did I do wrong here make the server can't receive the message ?
this my first time in network programming using java
Edit
I solve the NullPointerException the problem was that when client log out I didn't remove his socket from the ArrayList solved by making client before close send message contains quite so when I see it i remove his socket from array list Another Quetiosn Here i don't know how this message sentthe System.out.println() that is in the SendToAll function printed to the screen each time client send a message but why the message not send again to all clients ? actually the main problem is that server can't send the message to all clients in the array list after message comes from one client the problem not solved stell found
Client Code class
public class ClientSocket extends Thread {
public Socket socket = null;
public DataInputStream input = null;
public DataOutputStream output = null;
MainChat chat = null;
public ClientSocket(String ip, int port,MainChat ch) {
try {
socket = new Socket(ip,port);
input = new DataInputStream(socket.getInputStream());
output = new DataOutputStream(socket.getOutputStream());
chat = ch;
this.start();
}catch (IOException e){
}
}
#Override
public void run() {
while (true){
try {
String s = input.readLine();
if (!s.isEmpty()){
chat.WriteToScreen(s.trim());
}
}catch (IOException e){
}
}
}
public void WriteToSocket(String s) throws IOException{
output.write(s.getBytes());
}
}
Edit
when i use this code in main the SendToAll function send the message to all clients !! why when i use it from clients class using Thread it not sended to all ?
public static void main(String args[]){
int port = 5002;
Server server = new Server(port); // start server
//server.run(); // start connections wait for it
while (true) {
String s = in.next();
server.SendToAll(s + "\n"); // message sended to all client !!
}
}

The problem is that readLine reads until it finds a line terminator of end of file. This is why it works with other server in QT C++ but not with the Java server.
Please see here:
https://docs.oracle.com/javase/7/docs/api/java/io/DataInput.html#readLine()
https://docs.oracle.com/javase/7/docs/api/java/io/DataInputStream.html#readLine()
Please note that readLine in DataInputStream is deprecated. You should use BufferedReader to read a line (with readLine) as indicated in the DataInputStream link.
So, add '\n' to the end of the string sent and it will work.

I solve the problem, I am sorry for that it was my fault I forget to add \n in sendToAll function so this what cause the problem so no \n the clients can't read the line because I use readLine in DataInputStream
anyway I try another method to read bytes instead of readLine it's I think it's better especially when you receive UTF-8 char and after that changes from bytes to String

how to find tomcat server system information using java code?

i am developing web application and i host it in tomcat server. my requirement is client system wants to know the ip address of the system where the tomcat server located in a network.Before make any request to the server using java.or any possible to set default ip address for the tomcat server.and how can i use the default ip address to make a request if system ip and tomcat ip are different.

I don't know if I understood your question right. So the server is running in a local area network and your client software does not know which address/ip to connect to? You could add a multicast server to your servers app and a multicast receiver to your clients. The server will send a boardcast packet frequently to a specified boardcast address/channel, i.e. 203.0.113.0.
Once your client starts, it will receive the boardcast packet send by the server, as long as he is connected to the same channel. The packet is containing the servers address. You can than use that address to connect to the server.
Update
This is a very simplyfied example of a sender, receiver and a constants class to share the settings. It sends a String (Server is here) as packet data, but in a real world application, you should create an object serialize it at the server and deserialize it at the client. That object could hold more information about the server an could be verified at client side.
Server/Client side shared code:
public final class MulticastConstants {
public static final String MULTICAST_PACKET_DATA = "Server is here!";
public static final String MULTICAST_CHANNEL = "230.0.0.1";
public static final int MULTICAST_PORT = 8881;
public static final int MULTICAST_PACKET_SIZE = MULTICAST_PACKET_DATA.getBytes().length;
}
Server Side code:
The sender is a WebListener and will start and stop with your application.
#WebListener
public class MulticastSender implements ServletContextListener {
private MulticastSocket socket;
private boolean running = true;
private Thread mcss;
public MulticastSender() {
System.out.println("New " + this.getClass().getSimpleName());
try {
socket = new MulticastSocket(MulticastConstants.MULTICAST_PORT);
mcss = new MulticastServerThread();
} catch (IOException e) {
System.out.println("Error creating MulticastSender: " + e.getMessage());
}
}
#Override
public void contextInitialized(ServletContextEvent sce) {
System.out.println("Starting " + this.getClass().getSimpleName());
mcss.start();
}
#Override
public void contextDestroyed(ServletContextEvent sce) {
System.out.println("Stopping " + this.getClass().getSimpleName());
this.running = false;
socket.disconnect();
socket.close();
}
private class MulticastServerThread extends Thread {
public MulticastServerThread() {
super("MulticastServer");
}
public void run() {
System.out.println("Start sending multicast packets ...");
while (running) {
System.out.println("Sending multicast packet ...");
try {
byte[] dataBuffer = MulticastConstants.MULTICAST_PACKET_DATA.getBytes();
InetAddress group = InetAddress.getByName(MulticastConstants.MULTICAST_CHANNEL);
DatagramPacket packet = new DatagramPacket(dataBuffer, dataBuffer.length, group, MulticastConstants.MULTICAST_PORT);
socket.send(packet);
System.out.println("Packet send ...");
try {
sleep(2000);
} catch (InterruptedException e) {
}
} catch (IOException e) {
System.out.println("Error sending multicast packet: " + e.getMessage());
running = false;
break;
}
}
socket.close();
}
}
}
Client side code:
The client only receives a single packet for simplicity. You might create a thread to not to freeze your clients gui.
public class MulticastReceiver {
private MulticastSocket socket;
private InetAddress address;
public static void main(String[] args) throws InterruptedException {
new MulticastReceiver();
}
public MulticastReceiver() {
System.out.println("Starting MulticastReceiver ...");
try {
address = InetAddress.getByName(MulticastConstants.MULTICAST_CHANNEL);
socket = new MulticastSocket(MulticastConstants.MULTICAST_PORT);
socket.joinGroup(address);
DatagramPacket packet;
try {
byte[] buf = new byte[MulticastConstants.MULTICAST_PACKET_SIZE];
packet = new DatagramPacket(buf, buf.length);
System.out.println("Waiting for packets ...");
socket.receive(packet);
System.out.println("Received a packet (" + packet.getLength() + " bytes) ...");
// deserialize packet.getData() to your own object (for simplicity a String is used) ...
// check if type and serialVersionId are ok, otherwise dispose packet ...
System.out.println("Server is located at: " + packet.getAddress());
socket.close();
// connect to server ...
} catch (IOException ex) {
ex.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
} catch (UnknownHostException e) {
System.out.println("Could not connect to host \"" + address + "\": " + e.getMessage());
} catch (Exception e) {
System.out.println("Error initializing: " + e.getMessage());
}
}
}
Tested on Glassfish 4, hope that helps.

Sending data to sockets in an arraylist of Sockets

I have made a chat server that my clients can connect to but the clients don't get the messages the other sent. This is the code that does it all. Sending and receiving and setting up output streams.
public void run()
{
while(true)
{
for(int i = 0; i < ClientConnector.Connections.size(); i++)
{
try
{
if(Socket != null)
{
ObjectOutputStream Output = new ObjectOutputStream(Socket.getOutputStream());
ObjectInputStream Input = new ObjectInputStream(Socket.getInputStream());
whileChatting(Input, Output);
}
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
public static void sendMessage(String message, String returnedMessage, ObjectOutputStream out)
{
try
{
System.out.println("[Server] " + message);
if(!message.isEmpty())
{
out.writeObject("\247c[Server]\247d " + message);
out.flush();
System.out.println("[Chat] Sent: " + message);
}
else
{
out.writeObject(returnedMessage);
System.out.println("[Chat] Sent: " + returnedMessage);
}
out.flush();
System.out.println("[Info] Flushing remaining data to stream.");
}
catch(IOException ioException)
{
System.out.println("[Warning] Error: ioException # sendMessage line 76.");
}
}
public static void whileChatting(ObjectInputStream input, ObjectOutputStream output) throws IOException
{
String message = "";
do
{
try
{
message = (String) input.readObject();
System.out.println(message);
sendMessage("", message, output);
}
catch(ClassNotFoundException classNotFoundException)
{
System.out.println("[Warning] Error: ClassNotFoundException # whileChatting line 1-7.");
System.out.println("idk wtf that user sent!");
}
}while(!message.equals("/stop"));
}
I am wondering. How would i make this send what one person sends to all the clients? I keep a list of sockets in an array list of sockets. That looks like this.
public static ArrayList<Socket> Connections = new ArrayList<Socket>();
As each client connects it stores their Socket it this list. If there is a better way of doing this then please let me know.

If these are remote clients, then a MulticastSocket might do the trick. If these are local clients, then a publish/subscribe messaging service like HornetQ would work (clients subscribe to the message queue, and HornetQ takes care of the routing).

I don't see the point of the loop, when you don't make any use of the iteration variable. Surely you should be sending to ClientConnector.Connections.get(i)?
Another problem here is that you are creating a new ObjectInputStream and ObjectOutputStream on every iteration. That won't work. You must use the same pair of those streams per socket for the life of each socket, at both ends.

Writing a simple application to inject messages onto a queue

I'm trying to write a simple Java program to inject an MQ message onto a queue. I'm very inexperienced with writing to MQ queues using Java and have a couple of questions.
Can I connect to the unix queue on the unix box from my windows machine?
When I try to run the application I get a ....
java.lang.UnsatisfiedLinkError: no mqjbnd05 in java.library.path
From the sounds of what I could find in google I am missing some sort of resource. I'm thinking I'm getting this error possibly bc I'm not allowed to connect to the queue from windows?
Any good examples of how to achieve what I'm doing or help would be appreciated.
public class MQInject {
private MQQueueManager _queueManager = null;
private Hashtable params = null;
public int port = 1414;
public static final String hostname = "UQMYPOSIS1";
public static final String channel = "MQTX1012.MQTX1013";
public static final String qManager = "MQTX1013";
public static final String outputQName = "IIS.TLOG.5";
public MQInject(){
super();
}
public void init(){
//Set MQ connection credentials to MQ Envorinment.
MQEnvironment.hostname = hostname;
MQEnvironment.channel = channel;
MQEnvironment.port = port;
//MQEnvironment.userID = "";
//QEnvironment.password = password;
//set transport properties.
MQEnvironment.properties.put(MQC.TRANSPORT_PROPERTY, MQC.TRANSPORT_MQSERIES_CLIENT);
try {
//initialize MQ manager.
_queueManager = new MQQueueManager(qManager);
} catch (MQException e) {
e.printStackTrace();
}
}
public static void main(String[] args)
{
MQInject write = new MQInject();
try
{
write.selectQMgr();
write.write();
}
catch (IllegalArgumentException e)
{
System.out.println("Usage: java MQWrite <-h host> <-p port> <-c channel> <-m QueueManagerName> <-q QueueName>");
System.exit(1);
}
catch (MQException e)
{
System.out.println(e);
System.exit(1);
}
}
private void selectQMgr() throws MQException
{
_queueManager = new MQQueueManager(qManager);
}
private void write() throws MQException{
String line;
int lineNum=0;
int openOptions = MQC.MQOO_OUTPUT + MQC.MQOO_FAIL_IF_QUIESCING;
try {
MQQueue queue = _queueManager.accessQueue( outputQName,
openOptions,
null, // default q manager
null, // no dynamic q name
null ); // no alternate user id
DataInputStream input = new DataInputStream(System.in);
System.out.println("MQWrite v1.0 connected");
System.out.println("and ready for input, terminate with ^Z\n\n");
// Define a simple MQ message, and write some text in UTF format..
MQMessage sendmsg = new MQMessage();
sendmsg.format = MQC.MQFMT_STRING;
sendmsg.feedback = MQC.MQFB_NONE;
sendmsg.messageType = MQC.MQMT_DATAGRAM;
sendmsg.replyToQueueName = "ROGER.QUEUE";
sendmsg.replyToQueueManagerName = qManager;
MQPutMessageOptions pmo = new MQPutMessageOptions(); // accept the defaults, same
// as MQPMO_DEFAULT constant
while ((line = input.readLine()) != null){
sendmsg.clearMessage();
sendmsg.messageId = MQC.MQMI_NONE;
sendmsg.correlationId = MQC.MQCI_NONE;
sendmsg.writeString(line);
// put the message on the queue
queue.put(sendmsg, pmo);
System.out.println(++lineNum + ": " + line);
}
queue.close();
_queueManager.disconnect();
}catch (com.ibm.mq.MQException mqex){
System.out.println(mqex);
}
catch (java.io.IOException ioex){
System.out.println("An MQ IO error occurred : " + ioex);
}
}
}

For your first question, yes you can have a queue manager running on a UNIX host which is accessed by a client running on a Windows host.
For your second question, the mqjbnd05 library is only used to connect to the queue manager in binding mode (i.e. when the queue manager and the program accessing the queues are on the same host) and is not part of the MQ client installation. See http://www-01.ibm.com/support/docview.wss?uid=swg21158430 for more details. Looking through your code I can see that the init() function is specifying MQC.TRANSPORT_MQSERIES_CLIENT although I cannot see that the init() function is being called. Also it might be worth checking whether mqjbnd05 is specified in the library path and if so removing it.
Whilst probably not related to the error your getting, one other thing that might be worth checking is that the channel MQTX1012.MQTX1013 is a server connection channel as opposed to a sender or receiver channel.