We Keep Coding

java.net.SocketException Error. What am I doing wrong?

I created a SOA service with Socket Adapter on JDeveloper and I need to run/test it using Java. So I created a server class and a client class but I am getting an error
I did some research on how to create this service and test it and I came across some helpful material online but yet I'm getting an error and I dont know how to fix it. I am very new to making socket servers and stuff.
here is my server class
package client;
import java.net.ServerSocket;
import java.net.Socket;
public class Class1 {
try {
ServerSocket socket = new ServerSocket(12110);
Socket s=socket.accept();
System.out.println("Connected!");
} catch (Exception e) {
e.printStackTrace();
}
}
}
and here is my client class
package client;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.Socket;
public class Client{
public static void main(String[] args) {
try {
Socket socket = new Socket("localhost", 12110);
OutputStream os = socket.getOutputStream();
os.write("FirstName,LastName\nWaslley,Souza\nJohn,Snow".getBytes());
os.flush();
socket.shutdownOutput();
BufferedReader soc_in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String response = soc_in.readLine();
System.out.println("Response: " + response);
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
here is the error I get:
java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:210)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
at java.io.InputStreamReader.read(InputStreamReader.java:184)
at java.io.BufferedReader.fill(BufferedReader.java:161)
at java.io.BufferedReader.readLine(BufferedReader.java:324)
at java.io.BufferedReader.readLine(BufferedReader.java:389)
at client.Client.main(Client.java:23)

This happens because your server code exits after accepting a socket connection. Consequently, the JVM of this server will exit and (among others) close all socket connections it holds. This results in a SocketException on the client side.
To fix this, you should prevent the server's JVM from exiting, for instance by nesting the accept() call in a while loop:
public class Server {
public static void main(String[] args) {
try {
ServerSocket socket = new ServerSocket(12110);
while (true) {
Socket s = socket.accept();
System.out.println("Connected! to " + s);
}
} catch (final Exception e) {
e.printStackTrace();
}
}
}

Server Code:
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Class1 {
//static ServerSocket variable
private static ServerSocket server;
//socket server port on which it will listen
private static int port = 12110;
public static void main(String args[]) throws IOException, ClassNotFoundException {
//create the socket server object
server = new ServerSocket(port);
//keep listens indefinitely until receives 'exit' call or program terminates
while (true) {
System.out.println("Waiting for the client request");
//creating socket and waiting for client connection
Socket socket = server.accept();
//read from socket to ObjectInputStream object
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
//convert ObjectInputStream object to String
String message = (String) ois.readObject();
System.out.println("Message Received: " + message);
//create ObjectOutputStream object
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
//write object to Socket
oos.writeObject("Hi Client " + message);
//close resources
ois.close();
oos.close();
socket.close();
//terminate the server if client sends exit request
if (message.equalsIgnoreCase("exit")) {
break;
}
}
System.out.println("Shutting down Socket server!!");
//close the ServerSocket object
server.close();
}
}
Client Code:
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class Client {
public static void main(String[] args) throws UnknownHostException, IOException, ClassNotFoundException, InterruptedException {
//get the localhost IP address, if server is running on some other IP, you need to use that
InetAddress host = InetAddress.getLocalHost();
Socket socket = null;
ObjectOutputStream oos = null;
ObjectInputStream ois = null;
//establish socket connection to server
socket = new Socket(host.getHostName(), 12110);
//write to socket using ObjectOutputStream
oos = new ObjectOutputStream(socket.getOutputStream());
System.out.println("Sending request to Socket Server");
oos.writeObject("SEND SOME DATA");
//read the server response message
ois = new ObjectInputStream(socket.getInputStream());
String message = (String) ois.readObject();
System.out.println("Message: " + message);
//close resources
ois.close();
oos.close();
Thread.sleep(100);
}
}
do in this way.

yo #Mike sorry was not clear last time dig in this is the full server code
import java.net.ServerSocket;
import java.net.Socket;
import java.io.*;
public class Serv1 {
public static void main(String[] args) {
new Serv1().start();
}
public void start(){
String input = "";
try(ServerSocket socket = new ServerSocket(12110)) {
System.out.println("Connected!");
while (true) {
try(Socket server = socket.accept()){
BufferedReader in = new BufferedReader(new InputStreamReader(server.getInputStream(), "UTF-8"));
PrintStream echo = new PrintStream(server.getOutputStream());
while ((input = in.readLine()) != null && !input.equals(".")) {
System.out.println(input);
echo.println("Echoed: " + input);
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

This should do it
String input= "";
Socket server=socket.accept();
BufferedReader in = new BufferedReader(new InputStreamReader(server.getInputStream(), "UTF-8"));
PrintStream echo = new PrintStream(server.getOutputStream());
while((input = in.readLine()) != null && !input.equals(".")) {
System.out.println(input);
echo.println("echo: "+input);
}

Java client-socket:Cannot receive messages from server to client

So there this problem that has been giving me headaches for days now.I am making a multi-user chat application.My design is as follows:
1.There is a login window.
2.As soon as the details are entered, the client-side chat window opens.
3.Now the user starts typing.
4.As soon as he hits enter or clicks on the send button,the message is sent to the server.
5.The server sends it to all clients, including the one that send it the original message.
The problem:I am unable to receive any messages from the server to the client.
Here is my server class:
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class Server implements Runnable {
static InetAddress address;
static ArrayList<Integer> clients=new ArrayList<Integer>();
static ArrayList<Socket> socs=new ArrayList<>();
static String message="";
static DataOutputStream toClient;
static ServerSocket socket;
static Socket socketNew;
static boolean running=false;
public static void main(String[] args) throws IOException
{
socket=new ServerSocket(8000);
System.out.println("Server started on port 8000");
running=true;
while(true)
{
socketNew=socket.accept();
socs.add(socketNew);
address=socketNew.getInetAddress();
System.out.println("connected to client at address: "+address);
Server server=new Server();
new Thread(server).start();
}
}
public void run() {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(socketNew.getInputStream()));
String message;
PrintWriter out;
while ((message = br.readLine()) != null) {
System.out.println(message);
for (Socket s : socs) // sending the above msg. to all clients
{
out = new PrintWriter(s.getOutputStream(), true);
out.write(message);
out.flush();
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
And here is the receive_message function in the client class.Note that this method,I've run on a separate thread that starts as soon as the user logs-in.
public void receive_data()
{while(true)
{
try {
BufferedReader in;
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
while(in.readLine()!=null)
{
System.out.println(in.readLine());
console(in.readLine());
}
}
catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}
}
Any suggestions?Thanks for your time. :-)

You are writing messages without a line ending, while your client is waiting for a line ending character in the readLine loop. By placing out.write('\n') in your server send loop, it will also send a newline character.
Example:
for (Socket s : socs) {
out = new PrintWriter(s.getOutputStream(), true);
out.write(message);
out.write('\n'); // added this line
out.flush();
}

Java Server/Client string delay

i am creating a LAN game that accepts strings and parses them from structured english and displays them on a grid. i have created the server and client and it works but im having some issues. when i send a string it doesnt appear on the other machine right away. for some reason the string is only sent to the other machine once the other machine sends something over. i dont know why this happens. Could you please help me find out why it doesnt send straight away. Thanks
Server Code:
import java.awt.Point;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
public class studentServer{
static ServerSocket serverSocket;
static Socket socket;
static PrintWriter printWriter;
static BufferedReader bufferedReader;
static Thread thread;
Console console = new Console();
public ServerPlayergameMain gm;
public static void main(String args[]) throws Exception{
}
public void run(String commandMessage){
while(true){
try{
printWriter.println(commandMessage+"\n");
String input = bufferedReader.readLine();//reads the input from textfield
console.readLine("Client message: "+input);//Append to TextArea
}catch(Exception e){}
}
}
public void serverStartActionPerformed() {
System.out.println("Server has started!");
try{
serverSocket = new ServerSocket (8888); // socket for the server
socket = serverSocket.accept(); // waiting for socket to accept client
JOptionPane.showMessageDialog(null, "Your opponent has connected!", "Opponent Connection!", JOptionPane.INFORMATION_MESSAGE);
gm = new ServerPlayergameMain();
gm.setVisible(true);
bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream())); // reads line from input streamer
printWriter = new PrintWriter(socket.getOutputStream(),true);
}catch(IOException | HeadlessException e){
System.out.println("Server not running!"); //print message if server is not running
}
}
}
Client Code:
import java.io.*;
import java.net.*;
import javax.swing.JOptionPane;
public class StudentClient {
static Socket socket;
static PrintWriter printWriter;
static BufferedReader bufferedReader;
static Thread thread;
Console console = new Console();
public ClientPlayergameMain gm;
public void Clients(String address) {
try{
socket=new Socket("localhost",8888);//Socket for client
//below line reads input from InputStreamReader
bufferedReader=new BufferedReader(new InputStreamReader(socket.getInputStream()));
//below line writes output to OutPutStream
printWriter=new PrintWriter(socket.getOutputStream(),true);
JOptionPane.showMessageDialog(null, "Connected to server successfully", "Success", JOptionPane.INFORMATION_MESSAGE);
gm = new ClientPlayergameMain();
gm.setVisible(true);
System.out.println("Connected");//debug code
}catch(Exception e){
JOptionPane.showMessageDialog(null, "No Connection to server", "Error", JOptionPane.ERROR_MESSAGE);
System.out.println("Not Connected");
}
}
public static void run(String commandMessage){
while(true){
try{
printWriter.println(commandMessage+"\n");
String input = bufferedReader.readLine();
System.out.println("From server:" +input);
}catch(Exception e) {}
}
}
}
The code works but i dont know why there is a condition for the other machine to send something.
Thanks for your time.

A lot of compilation problems are there in you code. Some of the classes and objects are missing to resolve.
Still I have tried it to figure out the issue.
It may be the reasons:
sending new line character \n in printWriter.println(commandMessage+"\n"); statement, just remove \n.
client and server both are writing first in printWriter.println(commandMessage+"\n"); statement, make it last in anyone class
Here is the code:
StudentServer.java:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class StudentServer {
static ServerSocket serverSocket;
static Socket socket;
static PrintWriter printWriter;
static BufferedReader bufferedReader;
static Thread thread;
public static void main(String args[]) throws Exception {
StudentServer studentServer = new StudentServer();
studentServer.serverStartActionPerformed();
studentServer.run("server");
}
public void run(String commandMessage) {
if (true) {
try {
printWriter.println(commandMessage);
String input = bufferedReader.readLine();// reads the input from textfield
System.out.println("Client message: " + input);// Append to TextArea
} catch (Exception e) {
}
}
}
public void serverStartActionPerformed() {
System.out.println("Server has started!");
try {
serverSocket = new ServerSocket(8888); // socket for the server
socket = serverSocket.accept(); // waiting for socket to accept client
bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream())); // reads
// line
// from
// input
// streamer
printWriter = new PrintWriter(socket.getOutputStream(), true);
} catch (Exception e) {
e.printStackTrace();
System.out.println("Server not running!"); // print message if server is not running
}
}
}
StudentClient.java:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class StudentClient {
static Socket socket;
static PrintWriter printWriter;
static BufferedReader bufferedReader;
static Thread thread;
public void clients() {
try {
socket = new Socket("localhost", 8888);// Socket for client
// below line reads input from InputStreamReader
bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// below line writes output to OutPutStream
printWriter = new PrintWriter(socket.getOutputStream(), true);
System.out.println("Connected");// debug code
} catch (Exception e) {
System.out.println("Not Connected");
}
}
public void run(String commandMessage) {
if (true) {
try {
String input = bufferedReader.readLine();
System.out.println("From server:" + input);
printWriter.println(commandMessage);
} catch (Exception e) {
}
}
}
public static void main(String args[]) throws Exception {
StudentClient studentClient = new StudentClient();
studentClient.clients();
studentClient.run("client");
}
}

Have you tried printWriter.flush() after each write/print?

There are quite a few little problems, as Braj points out. The main one is in this sequence on your server side:
serverSocket = new ServerSocket (8888); // socket for the server
socket = serverSocket.accept(); // BLOCKS waiting for socket to accept client
// ..
printWriter = new PrintWriter(socket.getOutputStream(),true);
This means that printWriter, which you use to write to the client, doesn't even exist until after the server has listened for, blocked waiting on, and accepted a connection from the client.
If you want the connection to be opened for reading and writing without seeming to send anything from the client, send a handshake from the client. You could copy SMTP, and use HELO <myname>. That even tells the server who's calling.
Update after further reading:
I've always done like you have, and used the implicit connect that happens when you use getOutputStream() on the client side. However, Socket does allow you to connect an existing socket manually, using Socket#connect(). Try that, maybe it will work better than a handshake, for you.

Java TCP Client Server Hangs Up?

I am currently having difficulty understanding why my code is not working. I've included my client and server code below. I've figured out that my problem happens somewhere in the while loops but I'm not sure how to fix it so that it doesn't get stuck. I've searched around the forum for a while and some said adding a newline character would fix it, but I'm still having trouble.
My main question is how can I avoid the process from getting stuck and not communicating properly. Can anybody out there point me in the right direction?
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import java.net.UnknownHostException;
public class My_Client {
public static void main(String[] args) throws UnknownHostException, IOException {
Socket s = new Socket("localhost", 5555);
BufferedReader r = new BufferedReader(new InputStreamReader(
s.getInputStream()));
PrintStream w = new PrintStream(s.getOutputStream());
w.print("hello world");
w.print('\n');
String line;
while ((line = r.readLine()) != null) {
System.out.println("Received: " + line);
//System.out.println("Error");
}
w.close();
}
}
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
-----------------------------------------------------------------
public class My_Server {
private static final int PORT = 5555;
public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(PORT);
System.out.println("Server Socket Created");
while (true) {
System.out.println("Waiting on connection");
Socket cs = ss.accept();
System.out.println("Client connected");
BufferedReader r = new BufferedReader(new InputStreamReader(
cs.getInputStream()));
PrintStream w = new PrintStream(cs.getOutputStream());
String line;
while ((line = r.readLine()) != null) {
w.print(line + "!!!!");
w.print('\n');
}
System.out.println("Client disconnected");
r.close();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

Both ends are reading until EOS and neither is closing until after that. So you have a classic deadlock. You need to rethink your application protocol.
You also need to tell your PrintStream or PrintWriter to autoflush, or else call flush() yourself, but this is a relatively minor matter compared to the mistake above.

You should use autoflush on your PrintWriters like this:
PrintStream w = new PrintStream(cs.getOutputStream(),true);
You can setup a PROTOCOL to end the communication something like this:
In your client:
w.println("[END]");
In your server:
while (!(line = r.readLine()).equals("[END]")) {
Hope this helps:

Check the comments
And be sure that you get Client Connected on console of server side
CLIENT SIDE
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import java.net.UnknownHostException;
public class My_Client {
public static void main(String[] args) throws UnknownHostException, IOException {
Socket s = new Socket("localhost", 5555);
BufferedReader r = new BufferedReader(new InputStreamReader(
s.getInputStream()));
PrintStream w = new PrintStream(s.getOutputStream());
w.print("hello world");
w.print("\n"); // enter new line
w.flush();// flush the outputstream
String line;
while ((line = r.readLine()) != null) {
System.out.println("Received: " + line);
//System.out.println("Error");
}
w.close();
}
}
SERVER SIDE
----------------------------------------------------------
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
public class My_Server {
private static final int PORT = 5555;
public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(PORT);
System.out.println("Server Socket Created");
while (true) {
System.out.println("Waiting on connection");
Socket cs = ss.accept();
System.out.println("Client connected");
BufferedReader r = new BufferedReader(new InputStreamReader(
cs.getInputStream()));
PrintStream w = new PrintStream(cs.getOutputStream());
String line;
while ((line = r.readLine()) != null) {
w.print(line + "!!!!");
w.print("\n");// entering new line
}
System.out.println("Client disconnected");
r.close();
w.close();// close w
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

TCP socket communication failed after the first trial

I have received error message after the client side successful received one message from server side. The error message is: Exception in thread "main" java.net.SocketException: Software caused connection abort: recv failed
It seems in client class, line = inFromserver.readLine(); would not receive any message from server, making it become "null". But I dont know why. Could somebody please help me?
Server class
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
public class ConcurrentServer {
public static void main(String args[]) throws IOException
{
int portNumber = 20020;
ServerSocket serverSocket = new ServerSocket(portNumber);
while ( true ) {
new ServerConnection(serverSocket.accept()).start();
}
}
}
class ServerConnection extends Thread
{
Socket clientSocket;
PrintWriter outToClient;
ServerConnection (Socket clientSocket) throws SocketException
{
this.clientSocket = clientSocket;
setPriority(NORM_PRIORITY - 1);
}
public void run()
{
BufferedReader inFromClient;
try{
inFromClient = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
OutputStream outToClient = clientSocket.getOutputStream();
PrintWriter printOutPut = new PrintWriter(new OutputStreamWriter(outToClient),true);
String request= inFromClient.readLine();
if(request !=null)
{
if(!request.equalsIgnoreCase("finished"))
{
printOutPut.write("Receving data");
}
else
{
printOutPut.write("file received");
}
}
}catch (IOException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
try
{
clientSocket.close();
}catch (IOException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
}
}
client class
import java.io.*;
import java.net.*;
import java.util.concurrent.TimeUnit;
public class client{
public static void main(String[] args) throws Exception{
final int PORT=20020;
String serverHostname = new String("127.0.0.1");
Socket socket;
PrintWriter outToServer;
BufferedReader inFromServer;
BufferedReader inFromUser;
byte[] dataToTransfer;
String line;
int counter=0;
int i=0;
socket = new Socket(serverHostname, PORT);
outToServer = new PrintWriter(socket.getOutputStream(),true);
inFromServer = new BufferedReader(new InputStreamReader(socket.getInputStream()));
inFromUser = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Simulation of file transferring");
System.out.println("Enter the file size you want to transfer (Max Size 50MB)");
int userInput = Integer.parseInt(inFromUser.readLine());
System.out.println("Transferring start");
boolean connection = true;
while(connection)
{
//set transfer rate at 1MB/s
dataToTransfer = new byte[1000000];
Thread.sleep(1000);
if(i<userInput)
{
outToServer.println(dataToTransfer);
counter++;
System.out.println(counter + "MB file has been transferred");
}
else
{
outToServer.println("Finished");
}
line = inFromServer.readLine();
System.out.println(line);
if(!line.equalsIgnoreCase("file received"))
{
}
else
{
System.out.println("Transfer completed");
break;
}
i++;
}
outToServer.close();
inFromServer.close();
inFromUser.close();
socket.close();
}
}

You are sending byte array from client to server and reading string on server side.
Insert somthing in your byte array and then Convert your byte array into String
String str = new String(dataToTransfer,int offset, 1000000);
then write:
outToServer.println(str);