perdoname_
asked on
removemessage + readmessage / Client-Server app [problem with code]
Hello Experts,
I need your assistance about the following errors of a client/server application:
My current problem is that server reads the POSTMESSAGE command responds OK but in the case of READMESSAGE server doesn't give an answer back till it gets another command from the client
Also in the case of REMOVEMESSAGE it prints just ERROR.
---------------
Protocol:
Client’ Server: POSTMESSAGE message
Server’Client: If the list is not full, append message to the list and respond OK to the client.
Otherwise, respond ERROR
Client’ Server: READMESSAGE
Server’Client: If the list is empty, send ERROR. Otherwise: in case any of the messages in the list
(it doesnt matter which one) starts with URGENT:, send this message to the client and remove it
from the list. Otherwise, send the first message in the list to the client and remove it from the list.
Client’ Server: REMOVEMESSAGE message
Server’Client: If message is not contained in the list, send ERROR. Otherwise, remove it from
the list and send OK to the client.
Client’ Server: QUIT
Server’Client: Respond OK to the client and close the socket used to communicate with the
client.
Thanks in advance for any assistance !!
I need your assistance about the following errors of a client/server application:
My current problem is that server reads the POSTMESSAGE command responds OK but in the case of READMESSAGE server doesn't give an answer back till it gets another command from the client
Also in the case of REMOVEMESSAGE it prints just ERROR.
---------------
Protocol:
Client’ Server: POSTMESSAGE message
Server’Client: If the list is not full, append message to the list and respond OK to the client.
Otherwise, respond ERROR
Client’ Server: READMESSAGE
Server’Client: If the list is empty, send ERROR. Otherwise: in case any of the messages in the list
(it doesnt matter which one) starts with URGENT:, send this message to the client and remove it
from the list. Otherwise, send the first message in the list to the client and remove it from the list.
Client’ Server: REMOVEMESSAGE message
Server’Client: If message is not contained in the list, send ERROR. Otherwise, remove it from
the list and send OK to the client.
Client’ Server: QUIT
Server’Client: Respond OK to the client and close the socket used to communicate with the
client.
Thanks in advance for any assistance !!
//Server:
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.Vector;
public class ClientServerMsg {
static final int LISTENING_PORT = 4055;
public static void main(String[] args) throws Exception {
ServerSocket listener;
listener = new ServerSocket(LISTENING_PORT);
System.out.println("Port: " + LISTENING_PORT);
while (true) {
Socket connection = listener.accept();
new ConnectionHandler(connection);
}
}
static class ConnectionHandler extends Thread {
int MAX = 10;
Vector msgsList = new Vector();
Socket connection;
PrintWriter out = new PrintWriter(System.out, true); //For standard output
private OutputStream outstream;
ConnectionHandler(Socket conn) {
connection = conn;
start();
}
void sendPOSTMESSAGE(String msg) throws Exception {
try {
if (msgsList.size() < MAX) {
msgsList.addElement(msg);
out.println("OK");
out.flush();
} else {
out.println("ERROR");
out.flush();
}
} catch (Exception ex) {
out.println("ERROR");
out.flush();
}
if (out.checkError()) {
throw new Exception("Error while receiving the message");
}
}
void sendREADMESSAGE() throws Exception {
if (msgsList.size() == 0) {
out.println("ERROR");
out.flush();
} else if (msgsList.size() > 0) {
for (int i = 0; i < msgsList.size(); i++) {
if (((String) msgsList.elementAt(i)).startsWith("URGENT:")) {
out.write((String) msgsList.elementAt(i));
msgsList.remove(i);
} else {
out.write((String) msgsList.elementAt(0));
msgsList.remove(0);
}
}
} else {
if (out.checkError()) {
throw new Exception("Error");
}
}
}
void sendREMOVEMESSAGE(String remvmsg) throws Exception {
for (int i = 0; i < msgsList.size(); i++) {
if (((String) msgsList.elementAt(i)).equals(remvmsg)) {
msgsList.remove(i);
out.println("OK");
out.flush();
} else {
out.println("ERROR");
out.flush();
}
}
}
void sendQUIT() throws Exception {
out.close();
connection.close();
}
public void run() {
String command = "";
try {
InputStream instream = connection.getInputStream();
Scanner in = new Scanner(instream);
outstream = connection.getOutputStream();
//command = in.nextLine();
while ("QUIT".equals(command) == false) {
if (in.hasNextLine()) {
command = in.nextLine();
}
if (command.startsWith("POSTMESSAGE")) {
try {
sendPOSTMESSAGE(command);
} catch (Exception e) {
e.printStackTrace();
}
} else if (command.equals("READMESSAGE")) {
try {
sendREADMESSAGE();
} catch (Exception e) {
e.printStackTrace();
}
} else if (command.startsWith("REMOVEMESSAGE")) {
try {
sendREMOVEMESSAGE(command);
} catch (Exception e) {
e.printStackTrace();
}
} else if (command.equals("QUIT")) {
try {
sendQUIT();
} catch (Exception e) {
e.printStackTrace();
}
} else {
out.println("UNKNOWN COMMAND");
out.flush();
}
}
}catch(IOException e) {
e.printStackTrace();
} finally {
try {
connection.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
//Client:
//Client:
import java.io.*;
import java.net.*;
public class Client {
public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence = null;
String hostname;
int portNumber;
String portString;
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
System.out.println("What host would you like to connect to?");
hostname = inFromUser.readLine();
System.out.println("What port would you like to connect to?");
portString = inFromUser.readLine();
portNumber = Integer.parseInt(portString);
System.out.println("Connecting to port "+ portNumber+ " of "+ hostname +"....\n");
Socket clientSocket = new Socket(hostname, portNumber);
DataOutputStream outToServer =
new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer =
new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
System.out.println("Connection establised");
//sentence = inFromUser.readLine();
while (!(sentence = inFromUser.readLine()).equalsIgnoreCase("QUIT"))
{
/* send the sentence to the server */
outToServer.writeBytes(sentence + '\n');
// this line prevents the next message from user
//modifiedSentence = inFromServer.readLine();
outToServer.flush();
}
clientSocket.close();
}
}
You have the same question open already, wherein I suggested a new schematic for this.
ASKER CERTIFIED SOLUTION
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...and, i don't know how many times i've said not to use DataOutputStream in the client but to use PrintWriter. Your problem disappears for me after the two fixes i've mentioned
SOLUTION
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ASKER
But its not the same problem as before
Server now responds back to many messages:
ava ClientServerMsg localhost 4055
Port: 4055
OK
POSTMESSAGE messageOK
ERROR
ERROR
java Client
What host would you like to connect to?
localhost
What port would you like to connect to?
4055
Connecting to port 4055 of localhost....
Connection establised
POSTMESSAGE message
READMESSAGE
POSTMESSAGE msg
REMOVEMESSAGE POSTMESSAGE messageOK
REMOVEMESSAGE POSTMESSAGE message
Server now responds back to many messages:
ava ClientServerMsg localhost 4055
Port: 4055
OK
POSTMESSAGE messageOK
ERROR
ERROR
java Client
What host would you like to connect to?
localhost
What port would you like to connect to?
4055
Connecting to port 4055 of localhost....
Connection establised
POSTMESSAGE message
READMESSAGE
POSTMESSAGE msg
REMOVEMESSAGE POSTMESSAGE messageOK
REMOVEMESSAGE POSTMESSAGE message
ASKER
@CEHJ:
Thank you. READMESSAGE is solved
Any ideas about the sendREMOVEMESSAGE method?
Thank you. READMESSAGE is solved
Any ideas about the sendREMOVEMESSAGE method?
What's going wrong with that?
ASKER
For example:
//Client
POSTMESSAGE ok
REMOVEMESSAGE ok
and Server respodns back OK for the POSTMESSAGE but ERROR for the REMOVEMESSAGE
//Client
POSTMESSAGE ok
REMOVEMESSAGE ok
and Server respodns back OK for the POSTMESSAGE but ERROR for the REMOVEMESSAGE
ok - I've re-done your code so it works. I can post it over in the original question, but you'd need to deposit the points there for me, and of course it goes without saying for the help the other expert(s) gave you in this one. OK?
ASKER
Do you mean in this post ? or in that one: https://www.experts-exchange.com/questions/23308758/No-response-Server-code-attached.html ?
And I'll answer this point : ID:21324055Author:perdonam e_
here when we've done that.
(But I don't expect any points what I say in this question / post)
here when we've done that.
(But I don't expect any points what I say in this question / post)
ASKER
But only you have posted in that question so there is no problem with the points
OK - so your classes are about to appear over there.
(Of course I hope you saw from all this that your messages were being stored along with their protocols as well, making it extremely confusing). Thanks. k.