I have a server/client socket connection, each side can send a message to the other. The client who must begin the chat. I want to close the connection when one of the both sides (server and client) sends "quit" message.
here is my code:
import java.io.*;
import java.net.*;
class TCPClient {
public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence;
while(true){
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = new Socket("localhost", 6789);
DataOutputStream outToServer =
new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer =
new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
System.out.println("FROM SERVER: " + modifiedSentence);
if(modifiedSentence.equals("quit\n")) clientSocket.close();
}
}
}
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception
{
String clientSentence;
String sentence;
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
ServerSocket welcomeSocket = new ServerSocket(6789);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new
InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient =
new DataOutputStream(connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
System.out.println("FROM CLIENT: " + clientSentence);
//capitalizedSentence = clientSentence.toUpperCase() + '\n';
sentence = inFromUser.readLine();
outToClient.writeBytes(sentence);
}
}
}
Any help? :)
You have already written one line. Write another for "quit" and check this string when reading and close().
if you don't understand what you program is doing, use your debugger, that is what it is for.
Related
I have the following code below which is a very basic server. In the browser I put something like: localhost:6789/xxxx. When the app is running it does read the request from the client but then the message "This site can’t be reached" is displayed and the app throws an exception. What is the best way to respond to the client?
import java.net.*;
import java.io.*;
import java.net.Socket;
public class URLConnection {
public static void main(String[] args)throws IOException {
String clientSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);
while (true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
System.out.println("Received: " + clientSentence);
outToClient.writeBytes("HTTP/1.1 200 OK");
}
}
}
You have to close the OutputStream:
while (true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
System.out.println("Received: " + clientSentence);
outToClient.writeBytes("HTTP/1.1 200 OK");
outToClient.close();
}
Be aware that
the request may not necessarily be HTTP 1.1, and thus your response would be invalid.
there will actually be several clientSentence (i.e. consider adding a loop as below)
while (true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
while(true) {
clientSentence = inFromClient.readLine();
if (clientSentence != null && clientSentence.trim().isEmpty()) {
break;
} else {
System.out.println("Received: " + clientSentence);
}
}
outToClient.writeBytes("HTTP/1.1 200 OK\n\nHello world");
outToClient.close();
My TCP Client does not seems to be able to receive the data send from server after the connection is being accepted by the server.
I made the client initiate the connection, and I like it to work in this way.
loop:
client --> Server;
client <-- Server;
I am new to Java TCP socket programming, could somebody please enlighten me on how to make them work properly. Thanks and Appreciate help given in advance.
TCP Client Code:
import java.io.*;
import java.net.*;
class TCPClient
{
public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence;
BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
Socket clientSocket = new Socket("localhost", 6789);
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
while(true)
{
System.out.println("Message:");
sentence = inFromUser.readLine();
if(!sentence.equals("exit"))
{
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine(); //It does not receive any data from server.
System.out.println("FROM SERVER: " + modifiedSentence);
}
else
{
outToServer.writeBytes(sentence + '\n');
clientSocket.close();
break;
}
}
}
}
TCP Server Code:
import java.io.*;
import java.net.*;
import java.util.*;
class TCPServer
{
public static void main(String argv[]) throws Exception
{
String clientSentence;
String serverSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);
Socket connectionSocket;
connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
while(true)
{
clientSentence = inFromClient.readLine();
if(!clientSentence.equals("exit\n"))
{
System.out.println("Received: " + clientSentence);
System.out.println("Message:");
serverSentence = inFromUser.readLine();
outToClient.writeBytes(serverSentence); //able to send, but client is not receiving.
}
else
{
connectionSocket.close();
welcomeSocket.close();
}
}
}
}
Try to flush the data:
outToClient.writeBytes(serverSentence); //able to send, but client is not receiving.
outToClient.flush();
In the client you are closing the socket after sending data to the server. You need to keep it open.
while(true)
{
System.out.println("Message:");
sentence = inFromUser.readLine();
if(!sentence.equals("exit"))
{
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine(); //It does not receive any data from server.
System.out.println("FROM SERVER: " + modifiedSentence);
}
else
{
outToServer.writeBytes(sentence + '\n');
clientSocket.close(); //socket gets closed. Reopen it on the server side or remove that line
break;
}
}
After outToServer.writeBytes(sentence + '\n'); do outToServer.flush();
After outToClient.writeBytes(serverSentence + '\n'); do outToClient.flush();
My Issue based on code below:
Run TCPServer.java
then Run TCPClient.java
I expect to have the client print out
Server Said(1): HEY DUDE 1
Server Said(2): HEY DUDE 2
... but it just stays on HEY DUDE 1. What am I doing that is not producing the results I want?
TCPServer.java
import java.io.*;
import java.net.*;
class TCPServer {
public static void main (String args[]) throws Exception{
new TCPServer();
}
TCPServer() throws Exception{
//create welcoming socket at port 6789
ServerSocket welcomeSocket = new ServerSocket(6789);
while (true) {
//block on welcoming socket for contact by a client
Socket connectionSocket = welcomeSocket.accept();
// create thread for client
Connection c = new Connection(connectionSocket);
}
}
class Connection extends Thread{
Socket connectionSocket;
Connection(Socket _connectionSocket){
connectionSocket = _connectionSocket;
this.start();
}
public void run(){
try{
//create input stream attached to socket
BufferedReader inFromClient = new BufferedReader(new InputStreamReader (connectionSocket.getInputStream()));
//create output stream attached to socket
PrintWriter outToClient = new PrintWriter(new OutputStreamWriter(connectionSocket.getOutputStream()));
//read in line from the socket
String clientSentence = inFromClient.readLine();
System.out.println("Client sent: "+clientSentence);
//process
String capitalizedSentence = clientSentence.toUpperCase() + '\n';
//write out line to socket
outToClient.print(capitalizedSentence);
outToClient.flush();
}catch(Exception e){}
}
}
}
TCPClient.java
import java.io.*;
import java.net.*;
class TCPClient {
//String name="";
String host = "localhost";
int port = 6789;
Socket socket = null;
public static void main(String args[]) throws Exception{
TCPClient client = new TCPClient();
client.SendToServer("Hey dude 1");
System.out.println("Server Said(1): "+client.RecieveFromServer());
client.SendToServer("Hey dude 2");
System.out.println("Server Said(2): "+client.RecieveFromServer());
client.close();
}
TCPClient(String _host, int _port) throws Exception{
host = _host;
port = _port;
socket = new Socket(host, port);
}
TCPClient() throws Exception{
socket = new Socket(host, port);
}
void SendToServer(String msg) throws Exception{
//create output stream attached to socket
PrintWriter outToServer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));
//send msg to server
outToServer.print(msg + '\n');
outToServer.flush();
}
String RecieveFromServer() throws Exception{
//create input stream attached to socket
BufferedReader inFromServer = new BufferedReader(new InputStreamReader (socket.getInputStream()));
//read line from server
String res = inFromServer.readLine(); // if connection closes on server end, this throws java.net.SocketException
return res;
}
void close() throws IOException{
socket.close();
}
}
Your server thread ends as soon as you process first message. You need to put server code into a loop like this:
String clientSentence;
while ((clientSentence = inFromClient.readLine()) != null) {
System.out.println("Client sent: "+clientSentence);
//process
String capitalizedSentence = clientSentence.toUpperCase() + '\n';
//write out line to socket
outToClient.print(capitalizedSentence);
outToClient.flush();
}
Below is the code where there is a server to accept multiple client connections and respond. The server is able to receive the client's message but client is not receiving server messages. I have used multi threading concept on the server.
I also observed that nothing works (even a println statement) beyond line marked with ####. Could be that client is blocked.. Any thoughts?
server code:
public static void main(String argv[]) throws Exception
{
ServerSocket welcomeSocket = new ServerSocket(10000);
while(true)
{
Socket connectionSocket = welcomeSocket.accept();
Thread t = new Thread(new acceptconnection(connectionSocket));
t.start();}}
class acceptconnection implements Runnable{
BufferedReader inFromClient,inn;
DataOutputStream ds;
Socket clientsocket;
//constructor
acceptconnection (Socket socket) throws IOException{
this.clientsocket = socket;
inn = new BufferedReader (new InputStreamReader(System.in));
inFromClient =new BufferedReader(new InputStreamReader(clientsocket.getInputStream()));
ds = new DataOutputStream(clientsocket.getOutputStream());
public void run (){
try {
String clientSentence, inp;
while(( clientSentence = inFromClient.readLine())!=null)
{
System.out.println("from client" + clientSentence);
ds.writeBytes("hi from server");**// THIS DOES NOT WORK**
}
}
Client code:
public static void main(String argv[]) throws Exception
{
Socket clientSocket;
while(true)
{
// clientSock
clientSocket = new Socket("localhost", 10000);
BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
System.out.println("Enter something:");
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');// THIS WORKS - thats why server receives it
**####** modifiedSentence = inFromServer.readLine();**// THIS DOES NOT WORK -client unable to receive**
System.out.println("FROM SERVER: " + modifiedSentence + "remote sock add: "+ clientSocket.getRemoteSocketAddress());
As you're using BufferedReader.readLine() in your client, make sure to use a newline character when writing data out:
ds.writeBytes("hi from server\n");
And, as stated already, remember to flush...
ds.flush();
You should flush the stream on the server side
ds.writeBytes("hello world".getBytes());
ds.flush();
The exception is thrown in line 24 the second time I type something (after I have typed the host name) - server works right. Code
import java.io.*;
import java.net.*;
class TCPclient {
public static void main(String[] args) throws Exception {
String hostname, msg;
InetAddress hostaddress;
BufferedReader inFromUser = new BufferedReader (new InputStreamReader(System.in));
System.out.println("Please type host\n");
hostname = inFromUser.readLine(); //I type localhost
hostaddress = InetAddress.getByName(hostname);
Socket cSocket = new Socket(hostaddress, 44444);
String cAddress = cSocket.getLocalSocketAddress().toString();
DataOutputStream outToServer = new DataOutputStream (cSocket.getOutputStream());
while (true)
{
msg = inFromUser.readLine();
System.out.println(msg);
if (msg.equals("exit"))
{
System.out.println("exit");
break;
}
outToServer.writeBytes(cAddress + " said : " + msg + '\n'); //this line throws an exception the second time it runs
}
cSocket.close();
}
}
I am new in java so I am missing something obvious I guess. Exception reads :
Exception in thread "main"
java.net.SocketException: Software
caused connection abort: socket write
error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:115)
at java.io.DataOutputStream.writeBytes(DataOutputStream.java:259)
at TCPclient.main(TCPClient.java:52) Java
Result: 1
Server :
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception {
String clientSentence;
ServerSocket welcomeSocket = new ServerSocket(44444);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(
new InputStreamReader(connectionSocket.getInputStream( ) ) );
clientSentence = inFromClient.readLine();
System.out.println(clientSentence + "\n");
}
}
}
Your client creates one socket and writes over and over again to that one socket. Your server, on the other hand, does this:
ServerSocket welcomeSocket = new ServerSocket(44444);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
That accepts the incoming connection, reads one line, and then abandons it (and I'm guessing on the socket's finalize when being garbage collected it closes the connection). Then it waits for a new connection.
So to fix your immediate problem, try moving
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(
new InputStreamReader(connectionSocket.getInputStream( ) ) );
before the while loop.
How long do you wait between typing second line? It might have something to do with socket being idle.
Also with the server code like this you will see only first message. Try this:
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception {
String clientSentence;
ServerSocket welcomeSocket = new ServerSocket(44444);
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
while (true) {
clientSentence = inFromClient.readLine();
System.out.println(clientSentence + "\n");
}
}
}
Try:
while (true)
{
if(inFromUser.readLine() != null)
{
msg = inFromUser.readLine();
System.out.println(msg);
if (msg.equals("exit"))
{
System.out.println("exit");
break;
}
outToServer.writeBytes(cAddress + " said : " + msg + "\n");
}
}
Note the changes:
if(inFromUser.readLine() != null)
{
and
... "\n");
not
... '\n');
Give it a shot. It's probably too simple a solution, but it's something :)