I am naive to this socket programming. I am trying to print the content of the file present in the directory in the server's console but the server is not able to locate the file.
Here is my code:
myClient.java
import java.net.*;
import java.io.*;
public class myClient {
public static void main(String args[]){
Socket socket = null;
String hostName,command,fileName;
int port;
if(args.length == 0){
System.out.println("Error: command line arguments (hostname,port,command,"
+ "filename) not found.\nTry again...!!!");
System.exit(1);
}
hostName = args[0];
port = Integer.parseInt(args[1]);
command = args[2];
fileName = args[3];
try{
socket = new Socket(hostName,port);
System.out.println("Client Socket Created..!!");
// creating input and output streams to read from and write to the server
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
if(command.equals("GET")){
System.out.println("Client: GET "+fileName+" HTTP/1.1\n");
bw.write(fileName);
String line = br.readLine();
while(line != null){
System.out.println("Server: "+line);
line = br.readLine();
}
}
if(command.equals("PUT")){
System.out.println("Client: "+fileName+" sent to server");
bw.write(fileName);
// pass the file contents
bw.flush();
System.out.println("Server: "+br.readLine());
}
}
catch(UnknownHostException uhe){
System.out.println("Unknown Host...!!!");
System.exit(1);
}
catch(IOException e){
e.printStackTrace();
}
finally
{
//Closing the socket
try{
socket.close();
}
catch(Exception e){
e.printStackTrace();
}
}
}
}
myServer.java
import java.net.*;
import java.io.*;
public class myServer {
static Socket socket;
public static void main(String args[]){
try {
int port = Integer.parseInt(args[0]);
//String fileName = "";
ServerSocket server = new ServerSocket(port);
while(true)
{
System.out.println("Server started and listening on port "+port);
socket = server.accept();
System.out.println("received a connection :"+socket);
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write("Echo server 1.1\n");
bw.flush();
String line = br.readLine();
while(line != null){
bw.write("Echo: "+line);
bw.flush();
line = br.readLine();
}
}
} catch (IOException e) {
System.out.println("No conncetion established");
System.exit(0);
//e.printStackTrace();
}
finally
{
//Closing the socket
try{
socket.close();
}
catch(Exception e){
e.printStackTrace();
}
}
}
}
Kindly help me out finding a solution to this. I have tried many examples browsing different websites but not get to the solutions.
System.out.println("Client: GET "+fileName+" HTTP/1.1\n");
bw.write(fileName);
You aren't writing a correct HTTP command to the server. You're only sending the filename, not a complete command such as the GET command you're printing to the console.
The line terminator in HTTP is specified as \r\n, not \n.
You're also making no attempt to implement other aspects of HTTP 1.1 correctly, such as content-length. If you're going to implement HTTP you need a good knowledge of RFC 2616.
If possible you should throw this away and use HttpURLConnection.
Related
I'm trying to make a little chat system. I have a console and a client. Right now only the client need to send messages to the console. I can connect successfully to the server, and i can send one message from client to console. The trouble begins after sending the first message. When the first message i can't send any other messages.
I don't know if it's the console that won't read the message or the client that won't send the message. In this case how could i troubleshoot this?
public class ClientMainClass {
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);
Scanner scanner = new Scanner(System.in);
System.out.println("Skriv dit username:");
String name = scanner.nextLine();
System.out.println("Du er logget ind som: " + name);
String input;
do{
input = scanner.nextLine();
if (input.equalsIgnoreCase("exit")) {
System.out.println("Du forlod serveren");
socket.close();
continue;
}else {
/*OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);*/
PrintWriter printWriter = new PrintWriter(socket.getOutputStream(),true);
Date date = new Date();
String time = date.getDate()+"/"+date.getMonth()+":"+date.getHours()+":"+date.getMinutes();
//Send the message to the server
String message = time+ " - " + name + ": "+input;
printWriter.println(message);
System.out.println(message);
continue;
}
}while (!(input.equals("exit")));
} catch (Exception exception) {
exception.printStackTrace();
} finally {
//Closing the socket
try {
socket.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
My server:
public class Main{
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");
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);
System.out.println(br.readLine());
}
}
catch (Exception e) {
e.printStackTrace();
} finally {
try {
socket.close();
} catch(Exception e){}
}
}
}
To be clear. I can connect to the server. I can send one message from client to console, but no more than one message.
You never read a second line. Your Server accepts a connection, reads one line from that connection and then waits for a new connection, discarding everything that might arrive at the first connection.
Your client however sends all input using the first (and only) connection, which is absolutely correct.
This specific problem can be solved like this:
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);
while(true){
System.out.println(br.readLine());
}
}
This will cause your program to print everything arriving on that first connection, but it will never accept a second connection.
In order to handle multiple clients, you need a Thread to deal with each one.
I'm trying to build a simple server client program, I'm trying to figure a way how to prompt the CLIENT if the server is down, or if the server is up and loses connection
Question: How can I prompt the client that he's disconnected because the Server shuts down or loses connection
SERVER
public class Server{
private static Socket socket;
public static void main(String[] args)
{
try
{
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
//Server is running always. This is done using this while(true) loop
while(true)
{
//Reading the message from the client
socket = serverSocket.accept();
System.out.println("Client has connected!");
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();
}
}
CLIENT
public class Client{
private static Socket socket;
public static void main(String args[])
{
Scanner input=new Scanner(System.in);
while(true)
{
try
{
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket(address, port);
//System.out.println("You're now connected to the Server"); /*this should only print once */
//Send the message to the server
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
String number;
number=input.next();
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 (IOException exception)
{
//System.out.println("Server is still offline");/*This should only print once*/
}
How can I prompt the client that he's disconnected because the Server shuts down or loses connection?
You can use the catch block to prompt the client in Client class which will be executed when IOException occurs
} catch (ConnectException e) { //When the connection is refused upon connecting to the server
//promt the user here
System.out.println("Connection refused");
break; //to quit the infinite loop
} catch (IOException e) { //when connection drops, server closed, loses connection
//promt the user here
System.out.println("Disconnected from server");
break; //to quit the infinite loop
}
I have a client class and a server class.
If client sends message to server, server will send response back to the client, then client will print all the messages it received.
For example,
If Client sends "A" to Server, then Server will send response to client
"1111". So I use readLine() in client class to read the message from server, then client print "1111" in the console.
If Client sends "B" to Server, then Server will send response to client
"2222\n 3333". So the expected printing output from client is:
"2222"
"3333"
So the response message from server to client may have 1 line or 2 lines depending on the message it send from client to server.
My question is that how I can use readLine() to read the message that send from server to client. More specifically, if I use the following codes,
String messageFromServer;
while(( messageFromServer = inputStreamFromServer.readLine()) != null) {
println(messageFromServer);
}
It will only print the first line, and will not print anything else even if I keep sending message from client to server, because readLine() will stops once it has read the first line.
update:
More specifically, I am looking for some methods in the client class to read message that contains 1 or multiple lines from server at a time. I am wondering if there are any ways to do it in client side if I don't want to change the format of the message that sent from server to client.
update 2
To make my question more clear, I will put some sample codes in the following:
This is server:
import java.net.*;
import java.io.*;
public class Server {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(1234);
} catch (IOException e) {
System.err.println("Could not listen on port: 1234.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed.");
}
System.out.println("Connected");
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String textFromClient =null;
String textToClient =null;
textFromClient = in.readLine(); // read the text from client
if( textFromClient.equals("A")){
textToClient = "1111";
}else if ( textFromClient.equals("B")){
textToClient = "2222\r\n3333";
}
out.print(textToClient + "\r\n"); // send the response to client
out.flush();
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
}
The client:
public class Client {
public static void main(String[] args) throws IOException {
Socket socket = null;
PrintWriter out = null;
BufferedReader in = null;
BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
try {
socket = new Socket("localhost", 1234);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host");
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection");
}
System.out.println("Connected");
String textToServer;
while((textToServer = read.readLine())!=null){
out.print(textToServer + "\r\n" ); // send to server
out.flush();
String messageFromServer =null;
while(( messageFromServer = textToServer=in.readLine()) != null){
System.out.println(messageFromServer);
}
}
out.close();
in.close();
read.close();
socket.close();
}
private static void debug(String msg)
{
System.out.println("Client: " + msg);
}
}
You shouldn't need to change the format of the data sent by the server, and readLine() should work, but I suspect that the server is not flushing or closing the OutputStream after writing the response which could possibly explain things.
Is the call to readLine() hanging? Are you in control of the server code? If so, can you include it?
Revised classes that work as I believe you expect:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class ClientServerTest2
{
public static void main(String[] args) throws Exception
{
Thread serverThread = new Thread(new Server());
serverThread.start();
Thread clientThread = new Thread(new Client());
clientThread.start();
serverThread.join();
clientThread.join();
}
private static class Server implements Runnable
{
#Override
public void run()
{
ServerSocket serverSocket = null;
try
{
serverSocket = new ServerSocket(1234);
Socket clientSocket = null;
clientSocket = serverSocket.accept();
debug("Connected");
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String textFromClient = null;
String textToClient = null;
textFromClient = in.readLine(); // read the text from client
debug("Read '" + textFromClient + "'");
if ("A".equals(textFromClient))
{
textToClient = "1111";
}
else if ("B".equals(textFromClient))
{
textToClient = "2222\r\n3333";
}
debug("Writing '" + textToClient + "'");
out.print(textToClient + "\r\n"); // send the response to client
out.flush();
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
private static void debug(String msg)
{
System.out.println("Server: " + msg);
}
}
private static class Client implements Runnable
{
#Override
public void run()
{
Socket socket = null;
PrintWriter out = null;
BufferedReader in = null;
BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
try
{
socket = new Socket("localhost", 1234);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
debug("Connected");
String textToServer;
textToServer = read.readLine();
debug("Sending '" + textToServer + "'");
out.print(textToServer + "\r\n"); // send to server
out.flush();
String serverResponse = null;
while ((serverResponse = in.readLine()) != null)
debug(serverResponse); // read from server and print it.
out.close();
in.close();
read.close();
socket.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
private static void debug(String msg)
{
System.out.println("Client: " + msg);
}
}
Change while(( messageFromServer = inputStreamFromServer.readLine() != null) to while(( messageFromServer = inputStreamFromServer.readLine()) != null)
Actually this shouldn't even compile....
It's a work around.
If you want to send multiple strings like in your case : "2222\n 3333".
You can send them by adding a seperator character (like :) between two strings : "2222: 3333".
Then you can call write from server side as
clientOut.write("2222: 3333\n");
On client side parse recieved String :
messageFromServer = inputStreamFromServer.readLine();
String strArray[] = messageFromServer.split(":");
strArray[0] : 2222
strArray[0] : 3333
I am working on a java socket program and have difulcites with the client part. The server get's what all the clients write, but the client only gets what it writes. Could someone provide me with an example of a client part of a program that gets what all the clients write? Thanks!
Here is an "echo server" example
import java.io.*;
import java.net.*;
class TCPServer
{
public static void main(String argv[]) throws IOException
{
ServerSocket serverSocket = null;
DataInputStream serverInput = null;
PrintStream serverOutput = null;
String line = null;
Socket clientSocket = null;
// create server socket
try
{
serverSocket = new ServerSocket(2012);
clientSocket = serverSocket.accept();
serverInput = new DataInputStream(clientSocket.getInputStream());
serverOutput = new PrintStream(clientSocket.getOutputStream());
}
catch(IOException e){System.out.println(e);}
// receive data and send it back to the client
try
{
while(true)
{
line = serverInput.readLine();
if(line.equals("exit"))
{
break;
}
else
{
if(!line.equals(null) && !line.equals("exit"))
{
System.out.println("Received " +line);
line = line+" MODIFIED";
serverOutput.println(line);
}
}
}
}
catch(IOException e){System.out.println("SERVER SIDE: Unable send/receive data");}
try
{
serverInput.close();
serverOutput.close();
clientSocket.close();
serverSocket.close();
}
catch(IOException e){System.out.println(e);}
}
}
Here is the client
import java.io.*;
import java.net.*;
public class TCPClient
{
public static void main(String[] args) throws IOException
{
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
echoSocket = new Socket("localhost", 2012);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
} 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");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String userInput;
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
System.out.println("echo: " + in.readLine());
if(userInput.equals("exit"))
break;
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
}
}
I'm trying to use an InputStreamReader to read bytes sent by a socket
I have
InputStreamReader in = new InputStreamReader(socket.getInputStream());
in.read();
This throws an IOException :(. I know the socket should be sending something but it keeps throwing the error.
The actual error message and stack trace would indeed be useful.
You could try using a BufferedReader and using readLine to make sure you are getting something.enter link description here
import java.io.*;
import java.net.*;
public class EchoClient {
public static void main(String[] args) throws IOException {
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
echoSocket = new Socket("taranis", 7);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(
echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: taranis.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for "
+ "the connection to: taranis.");
System.exit(1);
}
BufferedReader stdIn = new BufferedReader(
new InputStreamReader(System.in));
String userInput;
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
System.out.println("echo: " + in.readLine());
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
}
}
Found here
That is expected behaviour, IOException is signalling that there is nothing to read, most probably socket has not connected properly. This question should be closed.