I am trying to write a simple and basic Java program where a client sends the server a string and the server is supposed to respond with a reversed string. I am sure I have the correct program structure and flow but my server is not read the string from my client. I have narrowed the problem to this line on the server side: string = inputStream.readLine();
Here is my code. What could be the problem?
Server1.java
import java.io.*;
import java.net.*;
class Server1 {
public static void main(String[] args) throws Exception {
String string = null;
ServerSocket myServerSocket = new ServerSocket(4000); //Create Socket
System.out.println("Server Running...");
Socket clientSocket = myServerSocket.accept();
DataInputStream inputStream = new DataInputStream(clientSocket.getInputStream());
PrintStream outputStream = new PrintStream(clientSocket.getOutputStream());
do {
string = inputStream.readLine();
if(string!=null){
//using StringBuilder method to reverse string
StringBuilder input = new StringBuilder();
// append a string into StringBuilder input1
input.append(input);
// reverse StringBuilder input1
input = input.reverse();
// print reversed String
for (int i = 0; i < input.length(); i++) {
outputStream.println(input.charAt(i));
}
}
} while (true);
/*outputStream.println("exit");
outputStream.close();
inputStream.close();
myServerSocket.close();
System.out.println("Server Closed!");*/
}
}
Client1.java
import java.io.*;
import java.net.*;
import java.util.Scanner;
class Client1 {
public static void main(String[] args) throws Exception {
Scanner sc = new Scanner(System.in); //Object to read keyboard input
String string = null, response = null; //Variable to store string
Socket mySocket = new Socket("127.0.0.1", 4000); //Create Socket
DataOutputStream outputStream = new DataOutputStream(mySocket.getOutputStream());
DataInputStream inputStream = new DataInputStream(mySocket.getInputStream());
System.out.println("Client Running...");
do {
System.out.println("Type in a string and Press Enter...");
string = sc.next();
outputStream.writeBytes(string);
response = inputStream.readLine();
if (response != null) {
System.out.println("Server Response: " + response);
}
} while (true);
}
}
The problem is that in this line string = inputStream.readLine();
it is searching for a line and if you wont add "\r\n" at the end of your massage it will keep searching for the lines end
I am trying to write a simple and basic Java program where a client
sends the server a string and the server is supposed to respond with a
reversed string. I am sure I have the correct program structure and
flow but my server is not read the string from my client. I have
narrowed the problem to this line on the server side: string =
inputStream.readLine(); Here is my code. What could be the problem?
Here, I can see copy paste mistake.
// append a string into StringBuilder input1
input.append(input);
Always use while(true) loop for reading message from the client,
Try below codes as for your question.
Server1.java
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class Server1 {
private static Socket socket;
public static void main(String[] args) {
try {
ServerSocket serverSocket = new ServerSocket(4000);
System.out.println("Server Running...");
//Note: Server is running always. This is done using this while(true) loop
while (true) {
//Reading the message from the client
socket = serverSocket.accept();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String string = br.readLine();
System.out.println("Message received from client is " + string);
//Reverse string responce builder
try {
//using StringBuilder method to reverse string
StringBuilder input = new StringBuilder();
// append a string into StringBuilder input
input.append(string);
// reverse StringBuilder input
input = input.reverse();
string = input + "\n"; //Next to line
// print reversed String
for (int i = 0; i < input.length(); i++) {
System.out.println(input.charAt(i));
}
} catch (Exception e) {
//Invalid text message back to client.
string = "Please send a proper text message\n";
}
//Sending the response back to the client.
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(string);
System.out.println("Message sent to the client is " + string);
bw.flush();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
socket.close();
} catch (Exception e) {
}
}
}
}
Client1.java
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.Scanner;
public class Client1 {
private static Socket socket;
public static void main(String args[]) {
try {
socket = new Socket("127.0.0.1", 4000);
System.out.println("Client Running...");
//Send the message to the server
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
System.out.println("Type in a string and Press Enter...");
Scanner sc = new Scanner(System.in);
String string = sc.next();
System.out.println("string = " + string);
String sendMessage = string + "\n"; ////Next to line
bw.write(sendMessage);
bw.flush();
System.out.println("Message sent to the server : " + sendMessage);
//Get the return message from the server
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String message = br.readLine();
System.out.println("Message received from the server : " + message);
} catch (Exception exception) {
exception.printStackTrace();
} finally {
//finally close the socket
try {
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
Related
I have been working on creating a program where communication can be exchanged between a server and a client using to program files in java. However, when I try to send messages from server to client. I have been working on a project where I am trying to send a message from a server to a client. However, when I put in my message, from the server, the client seems to get stuck on sentence = inFromServer.readLine(); in the client portion of my code and I'm not sure why. I ran the debugger on this, and it seems that "sentence" takes in the value that was inputted from the client, so im not sure why it get stuck. Does anyone have an idea what the problem may be?
Here's my code for reference-
Server Code:
package com.company;
import java.io.*;
import java.net.*;
import java.util.Scanner;
import java.util.concurrent.*;
import java.io.IOException;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
class threading implements Runnable {
private int portnumbers;
Socket clientsocket;
ServerSocket connectorsocket;
public threading(Socket clientsocket)
{
this.clientsocket = clientsocket;
}
public void run(){
try {
Serverstuff(this.clientsocket);
}
catch(Exception ex)
{
System.out.print("I found exception" + ex);
}
}
public void Serverstuff(Socket socketlol)
{
// File h = null;
int width = 1536;
int height = 2048;
BufferedImage image = null;
File f = null;
while(true) {
try {
String sentence1;
//Wait on welcoming socket for client
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(socketlol.getInputStream()));
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
DataOutputStream outToClient = new DataOutputStream(socketlol.getOutputStream());//create input stream, attached to socket
System.out.println("Flag1");
sentence1 = inFromUser.readLine();
System.out.println("Flag2");
System.out.println("Flag3");
outToClient.writeBytes(sentence1);
}
catch(Exception ex)
{
System.out.print("I found exception" + ex);
}
}
}
}
public class server{
public static void main(String argv[]) throws Exception {
String clientSentence;
String capitalizedSentence;
int portnumber;
Scanner scanney = new Scanner(System.in);
System.out.println("Enter the number of clients");
String arg1 = scanney.next();
int arg2 = Integer.parseInt(arg1);
int[] socketarray = new int[arg2];
for(int i = 0; i < arg2; i++) {
System.out.println("enter the port number");
String portnumberstr = scanney.next();
portnumber = Integer.parseInt(portnumberstr);
socketarray[i] = portnumber;
}
//ServerSocket welcomeSocket = new ServerSocket(5000);
int g = 0;
int whatever;
//ServerSocket welcomeSocket2 = new ServerSocket(5001);
while (true) {
if(g < arg2) {
System.out.println("Flagwhile1");
whatever = socketarray[g];
ServerSocket welcomeSocket = new ServerSocket(whatever);
System.out.println("Flagwhile2");
Socket clientsock = welcomeSocket.accept();
threading newthread = new threading(clientsock);
System.out.println("Flagwhile3");
new Thread(newthread).start();
g = g + 1;
}
}
}
}
Client Code:
package com.company;
import java.io.*;
import java.net.*;
import java.util.Scanner;
import java.util.concurrent.*;
import java.io.IOException;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
public class client2{
public static void main(String argv[]) throws Exception {
try {
String sentence;
String modifiedSentence;
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in)); //Create input stream
Socket clientSocket = new Socket("127.0.0.2", 5001); //Create client socket connect to server
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream()); //Create output stream, attached to socket
System.out.println("Flag19");
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); //Create input stream attached to socket
System.out.println("Flag20");
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n'); //send line to server
System.out.println("Flag21");
sentence = inFromServer.readLine();
System.out.println("Flag22");
System.out.println(sentence);
int test = 5;
clientSocket.close();
}
catch(IOException e){
System.out.println("Error: " + e);
}
}
}
I am learning Java and I'm writing an example client - server application.
The sokcket connection is fine, everything works well until the second message from the client app. It does not reach the server. If I start another client it also succeed at the first message, and fails at the second.
Anyone has an idea? Thanks in advance!
Server code:
package networking;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
private static Socket socket;
public static void main(String[] args) {
try {
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Server Started and listening to the port 25000");
//Server is running always. This is done using this while(true) loop
while (true) {
//Reading the message from the client
socket = serverSocket.accept();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String incomingMessage = br.readLine();
System.out.println("((( " + incomingMessage);
String returnMessage = incomingMessage;
//Sending the response back to the client.
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returnMessage + "\n");
bw.flush();
System.out.println("))) " + returnMessage);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
socket.close();
} catch (Exception e) {
}
}
}
}
And the client
package networking;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class Client {
private static Socket socket;
public static void main(String args[]) {
try {
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket(address, port);
//Send the message to the server
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String message = "";
/*
while(!message.equals("q")) {
System.out.print("Message: ");
message = console.readLine();
bw.write(message + "\n");
bw.flush();
System.out.println("))) " + message);
//Get the return message from the server
String incomingMessage = br.readLine();
System.out.println("((( " + incomingMessage);
}
*/
for (int i = 0; i < 10; i++) {
bw.write(i + "\n");
bw.flush();
System.out.println("))) " + i);
String incomingMessage = br.readLine();
System.out.println("((( " + incomingMessage);
}
} catch (Exception exception) {
exception.printStackTrace();
} finally {
//Closing the socket
try {
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
Your while is misplaced in your server code, and in fact you need 2 while loops:
one for accepting new clients
one for manage several messages by client
In pseudo code it gives you:
while (true):
accept new client
while (client connected):
read message from client
write back message to client
close client socket
If you want to use threads, then it's the inner while loop task which you have to delegate to a new thread.
Note: accept is blocking until a new client comes. That why you could send only one message by client.
Your server is not set up to handle this. You are reading one line, then discarding the connection for the GC, without closing it. The server, reading one line, then ignores all other lines and starts listening for the next connection.
Also, consider using threads.
server class :
the program is about to receive data from client and then reply. the server is okay..., but the problem is when the server send the reply to the client. the client always says 'the socket is close'. i try to delete secket close statement but the result is same.., the output says that 'the socket is close'. so please help me to solve this problem...
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;
public class Nomor3Server {
public static final int SERVICE_PORT = 2020;
public static void main(String[] args) {
try {
ServerSocket server = new ServerSocket(SERVICE_PORT);
System.out.println("DAytime service started");
for (;;) {
Socket nextClient = server.accept();
BufferedReader pesan = new BufferedReader(new InputStreamReader(nextClient.getInputStream()));
String messageIn = pesan.readLine();
System.out.println("Received request from "
+ nextClient.getInetAddress() + " : "
+ nextClient.getPort()
+ "\nIsi Pesan : " + messageIn);
String messageOut = "انا لا ادر";
switch (messageIn) {
case "saya":
messageOut = "أنا";
break;
case "kamu":
messageOut = "أنت";
break;
default:
break;
}
OutputStream out = nextClient.getOutputStream();
PrintStream pout = new PrintStream(out);
pout.print(messageOut);
out.flush();
out.close();
System.out.println("Message sent");
//nextClient.close();
}
} catch (BindException e) {
System.err.println("Server Already Running on port : " + SERVICE_PORT);
} catch (IOException ioe) {
System.err.println("error : " + ioe);
}
}
}
client class :
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.Socket;
public class Nomor3Client {
public static final int SERVICE_PORT = 2020;
public static void main(String[] args) {
try {
String hostname = "localhost";
System.out.println("Connection Established");
//for (;;) {
System.out.println("Enter Your Message : ");
BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
String pesan = read.readLine();
Socket daytime = new Socket(hostname, SERVICE_PORT);
if (pesan.equals("exit")) {
System.exit(0);
} else {
daytime.setSoTimeout(2000);
OutputStream out = daytime.getOutputStream();
PrintStream pout = new PrintStream(out);
pout.print(pesan);
out.flush();
out.close();
BufferedReader messageIn = new BufferedReader(new InputStreamReader(daytime.getInputStream()));
System.out.println("Respond : " + messageIn.readLine());
System.out.println("diterima");
}
daytime.close();
//}
} catch (IOException e) {
System.err.println("Error : " + e);
}
}
}
OutputStream out = daytime.getOutputStream();
PrintStream pout = new PrintStream(out);
pout.print(pesan);
out.flush();
out.close();
https://docs.oracle.com/javase/7/docs/api/java/net/Socket.html#getOutputStream()
Closing the returned OutputStream will close the associated socket.
Socket get closed in such situations:
when you close the socket,
when you close the input or the output socket stream,
when you close the object, which is directly or indirectly wrapping the input or the output socket stream, e.g. BufferedReader or Scanner.
Server Class
OutputStream out = nextClient.getOutputStream();
PrintStream pout = new PrintStream(out);
pout.print(messageOut);
out.flush();
out.close(); //Don't close this
Client Code :
OutputStream out = daytime.getOutputStream();
PrintStream pout = new PrintStream(out);
pout.print(pesan);
out.flush();
out.close(); //Don't close this
I want to implement any one sorting algorithm using TCP/UDP on Server application and Give Input On Client side and client should sorted output from server and display sorted on input side. Here, I have created program for multiplication of a number. I am not getting how to pass int array from client side and receive the same array. How can I do that.It would be a great help. Thank in advance.
Client.java
package sorting_app;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.InetAddress;
import java.net.Socket;
public class Client
{
private static Socket socket;
public static void main(String args[])
{
try
{
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket(address, port);
//Send the message to the server
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
String number = "2";
String sendMessage = number + "\n";
bw.write(sendMessage);
bw.flush();
System.out.println("Message sent to the server : "+sendMessage);
//Get the return message from the server
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String message = br.readLine();
System.out.println("Message received from the server : " +message);
}
catch (Exception exception)
{
exception.printStackTrace();
}
finally
{
//Closing the socket
try
{
socket.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
}
Server.java
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class Server
{
private static Socket socket;
public static void main(String[] args)
{
try
{
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Server Started and listening to the port 25000");
//Server is running always. This is done using this while(true) loop
while(true)
{
//Reading the message from the client
socket = serverSocket.accept();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String number = br.readLine();
System.out.println("Message received from client is "+number);
//Multiplying the number by 2 and forming the return message
String returnMessage;
try
{
int numberInIntFormat = Integer.parseInt(number);
int returnValue = numberInIntFormat*2;
returnMessage = String.valueOf(returnValue) + "\n";
}
catch(NumberFormatException e)
{
//Input was not a number. Sending proper message back to client.
returnMessage = "Please send a proper number\n";
}
//Sending the response back to the client.
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returnMessage);
System.out.println("Message sent to the client is "+returnMessage);
bw.flush();
}
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
try
{
socket.close();
}
catch(Exception e){}
}
}
}
BufferedReader and BufferedWriter are for character streams.
Consider using other ways, like ObjectInputStream and ObjectOutputStream.
(DataOutputStream / DataInputStream could be good too)
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);