I'm learning some Java socket programming and I've managed to make my first ever connection between Server and Client. That sparked a curiosity in me: what would happen if instead of the "Connected" and "Message Received" messages I made a sort of "chat room" type thing, where server and client inputs are printed to one another? So I tried doing just that.
Now, I know this isn't the way chat rooms are created (I'd probably need Threads and whatnot), but I was very curious as to why this didn't work:
Server:
public void run() throws Exception
{
boolean isChatting = true;
Socket clientSocket = new Socket("localhost", 444);
PrintStream ps = new PrintStream(clientSocket.getOutputStream());
ps.println("Connected.");
BufferedReader bfr = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
BufferedReader bfrClient = new BufferedReader(new InputStreamReader(System.in));
String serverMessage = bfr.readLine();
String clientMessage;
System.out.println("Server: "+serverMessage);
while (isChatting)
{
clientMessage = bfrClient.readLine();
ps.println(clientMessage);
if (clientMessage.toUpperCase().equals("EXIT"))
{
isChatting = false;
}
}
bfr.close();
bfrClient.close();
}
Client:
public void run() throws Exception
{
boolean isChatting = true;
ServerSocket server = new ServerSocket(444); //Port
Socket sSocket = server.accept();
PrintStream ps = new PrintStream(sSocket.getOutputStream());
BufferedReader bfr = new BufferedReader(new InputStreamReader(sSocket.getInputStream()));
BufferedReader bfrPersonal = new BufferedReader(new InputStreamReader(System.in));
String clientMessage = bfr.readLine();
String messageToSend;
System.out.println("Client: "+clientMessage);
if (clientMessage != null)
{
ps.println("Connected.");
}
while (isChatting)
{
messageToSend = bfrPersonal.readLine();
ps.println(messageToSend);
if (messageToSend.toUpperCase().equals("EXIT"))
{
isChatting = false;
}
}
bfr.close();
bfrPersonal.close();
}
Thank you for your time! :)
If you like to create a chat system the easiest way is to create two threads on the server and two threads on the client side.
The first thread handle the input of the user and send it.
The second thread handle the input from the other chat system and print it.
Related
I'm working on a basic Client-Server connection.
This code works perfectly yet the client can only send 1 message and receive its modification before closing the connection.
how can I make it to send and receive multiple messages?
I thought of using a while loop yet I didn't know how to implement it correctly.
I need to be able to send more than 1 message in order to have a consistent connection
The code below is a client sending a string to the server and the server turns it to uppercase.
//Server:
public class TCPServer {
public static void main(String argv[]) throws Exception
{
String clientSentence;
String capitalizedSentence;
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();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeBytes(capitalizedSentence);
if(clientSentence.toUpperCase().trim().contentEquals("QUIT")) {
connectionSocket.close();
}
}
}
}
//Client:
public class TCPClient {
public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence;
Socket clientSocket = new Socket("LocalHost", 6789);
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
System.out.print("Enter characters to be capitalized: ");
sentence = inFromUser.readLine();
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
System.out.println("FROM SERVER: " + modifiedSentence);
}
}
the output for this code is:
Enter characters to be capitalized: hi
FROM SERVER: HI
Your Server can gets only one message from each client, because in your while-loop, in each iteration you call to welcomeSocket.accept(). This means that your server code stops until it gets new client connection.
Consider to use multi-threading if you want your server will support multiple clients. For example, take a look: on this post
I want to send objects from the server to the client in java sockets. I can send them from client to the server, however I am struggling to send them from server to client. I am new to Java so I'm still learning the basics. I know its something relatively minor that I need to do, however i am struggling with it at the moment. Can someone add the bits of code that i am missing?
Open another connection in another thread and let the client be server, and server be client. So in one thread you send A -> B, in another thread you open another socket and begin to send b B -> A.
The problem with low level sockets is that if one side is writing, the other should be listening. That means you have to implement command-query protocol, which is a heavy task. So with my proposal you will use two ports but you know that you will have 2 pipes of data flow.
A --8888--> B
A <--8889-- B
It will be easier if you are just starting with sockets.
You can use ObjectOutputStream to send an object through the socket and ObjectInputStream to receive one:
private ObjectOutputStream oos;
private ObjectInputStream ois;
public SocketHandler(Socket cs) {
this.oos = new ObjectOutputStream(cs.getOutputStream());
this.ois = new ObjectInputStream(cs.getInputStream());
}
public void sendObject(Object o) {
this.oos.writeObject(o);
this.oos.flush();
}
public Object receiveObject() {
return this.ois.readObject();
}
That was assuming you want to send and receive an Object. You can also use PrintWriter and BufferedReader to send and receive String messages and after parsing it:
private PrintWriter pw;
private BufferedReader br;
public SocketHandler(Socket cs) {
this.pw = new PrintWriter(cs.getOutputStream());
this.br = new BufferedReader(new InputStreamReader(cs.getInputStream()));
}
public void sendMsg(String msg) {
this.pw.println(msg);
this.pw.flush();
}
public String receiveMsg() {
return this.br.readLine();
}
Below I have an example of some Server-Side code that I used for an application a while ago, then I will give you an explanation as to what's going on here:
first you need to create your ServerSocket in order to accept client requests (as you already know):
ServerSocket serverSocket = new ServerSocket(1002);
while(true) {
Then you need to enter a while loop in order to receive requests for as long as the Server program is alive
Socket clientSocket = serverSocket.accept();
System.out.println("Connection made to: " + clientSocket);
BufferedReader br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
String messageString = "";
String line;
System.out.println("Enter while loop to retrieve client message...");
while((line = br.readLine()) != null) {
String clientRequestLine = line;
if(clientRequestLine.contains("check return user credentials")) {
String userNamePassWord = clientRequestLine.replace("check return user credentials", "");
userNamePassWord = userNamePassWord.trim();
String[] userNamePassWordSplitter = userNamePassWord.split(" ");
String userName = userNamePassWordSplitter[0];
String passWord = userNamePassWordSplitter[1];
System.out.println("Username: " + userName + "\nPassword: " + passWord);
boolean isValidUserNamePassWord = ReturnPatientCredentials.checkUserNamePassWord(userName, passWord);
if(isValidUserNamePassWord) {
System.out.println("valid");
out.println("valid");
}
else {
System.out.println("invalid");
out.println("invalid");
}
}
Above you need to start a BufferedReader in order to store an InputStream (the data) from the client socket. You also need to create a PrintWriter so that you can send data to the OutputStream and you need to pass your clientSocket as the argument for the OutputStream. Next you'll create variables to get the message and the "line" of date from the client and enter a while loop. You can then store the line in a variable and read the data or whatever you need to do. We use our PrintWriter (out) to send data back with the println() method and then we can break out of the loop when needed.
I am new to socket programming. I have to write a program where client accepts filename from a user and sends it to the server. The server reads corresponding file and sends its content back to client. Now my problem is server program freezes on 'String file = br.readLine()'. When I terminate my client program, further lines of server code get executed. If I comment out while loop at the end of my client code, server code works perfectly fine(it prints data to standard output). Can you tell what could be wrong with my code?
Server Code:
public class SocketServer {
public static void main(String[] args) throws Exception{
System.out.println("Server is started.");
ServerSocket ss = new ServerSocket(9999);
System.out.println("Server is waiting for a client.");
Socket server = ss.accept();
System.out.println("Client is connected.");
BufferedReader br = new BufferedReader(new InputStreamReader(server.getInputStream()));
String file = br.readLine();
System.out.println("Requested file is: " + file);
OutputStreamWriter os = new OutputStreamWriter(server.getOutputStream());
PrintWriter writer = new PrintWriter(os);
BufferedReader fr = new BufferedReader(new FileReader(file));
String line;
while((line = fr.readLine()) != null) {
writer.write(line);
writer.flush();
System.out.println(line);
}
}
}
Client Code:
public class SocketClient {
public static void main(String[] args) throws Exception {
Scanner in = new Scanner(System.in);
Socket client = new Socket("localhost", 9999);
OutputStreamWriter os = new OutputStreamWriter(client.getOutputStream());
PrintWriter writer = new PrintWriter(os);
System.out.print("Enter filename: ");
String file = in.nextLine();
writer.write(file);
writer.flush();
BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
System.out.println("Content of " + file + ":");
String str;
while((str = br.readLine()) != null) {
System.out.print(str);
}
System.out.println("File transfer is complete.");
}
}
br.readLine(); will wait for input till it finds a new-line .
writer.write(file); You are writing file name without a new-line.
So in order to make it work either write a newline char at client or read it char by char at server.
Hope this helps.
I am trying to make a socket server, I am connecting through putty to this server. Whenever I type "hi" it says "no" rather than "hi" which I want it to do. I found this on A java website. If you could tell me what I am doing wrong that would be great. Thanks!
int port = 12345;
ServerSocket sock = new ServerSocket(port);
System.out.println("Server now active on port: " + port);
Socket link = sock.accept();
System.out.println("Interface accepted request, IP: " + link.getInetAddress());
BufferedReader input = new BufferedReader(new InputStreamReader(link.getInputStream()));
PrintWriter output = new PrintWriter(link.getOutputStream(), true);
output.println("ISEEYOU");
String inputLine;
Thread.sleep(1500);
while((inputLine = input.readLine()) != null) {
if(inputLine.equals("hi")) {
output.println("hi");
}else{
output.println("no");
}
}
Your Java program is correct.
I've tried your code, just added System.out.printf("[%s]", inputLine); as first line in the while loop to ensure, what I get from putty.
I guess your problem is the protocol putty uses to connect. It worked with RAW for me. See below the session setting I've used:
EDIT:
According to your comment I added some code for a simple client, that reads the line from console, sends it to the server and prints the echo back to console.
public void Client() throws IOException {
// Client that closes the communication when the user types "quit"
Socket socket = new Socket("localhost", 8080);
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintStream ps = new PrintStream(socket.getOutputStream());
BufferedReader user = new BufferedReader(new InputStreamReader(System.in));
String line;
while(!(line = user.readLine()).equals("quit")) {
ps.println(line); // Write to server
System.out.println(reader.readLine()); // Receive echo
}
socket.shutdownOutput(); // Send EOF to server
socket.close();
}
The corresponding server would look like this:
public void server() throws IOException {
ServerSocket serverSocket = new ServerSocket(8080);
Socket socket = serverSocket.accept();
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintStream ps = new PrintStream(socket.getOutputStream());
// Just read a line and echo it till EOF
String line;
while((line = reader.readLine()) != null) ps.println(line);
}
You might need to change the port I used here, if 8080 is already binded on your machine. Also you might want to have the server running on another computer then the client. In this case you need to change "localhost".
So I am trying to have a sever sit and listen waiting for a connection from a client. The client sends over some string and the sever does some action based on whats received. Now what I would like to happen is the client sends over some command asking for data back and have the server get what it needs to and send the string back.
Not a big deal right? Well for some reason I can't get it working, my best guess is that its not closing the socket properly. I can't figure out why it wouldn't or what I am doing wrong.
Client
String data = "";
DataOutputStream outToServer = null;
BufferedReader input;
try {
outToServer = new DataOutputStream(clientSocket.getOutputStream());
outToServer.writeBytes("GETDATA");
outToServer.flush();
input = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
data = input.readLine();
Log.d("ANSWER: ", data);
input.close();
} catch (IOException e) {
Log.d("Error: ", e.toString());
}
Server
ServerSocket listeningSocket = new ServerSocket(9008);
BufferedReader fromClient ;
PrintStream os;
while(true) {
Socket clientSocket = listeningSocket.accept();
ServerConnection clientConnection = new ServerConnection(clientSocket);
os = new PrintStream(clientSocket.getOutputStream());
fromClient= new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
if(fromClient.readLine().equals("GETDATA")){
os.println("DATA");
os.flush();
clientSocket.wait();
clientSocket.close();
}
else{
clientConnection.run();
}
}
Any ideas?
here is your error
outToServer.writeBytes("GETDATA");
the right code is
outToServer.writeBytes("GETDATA\n");
as your using readline you should send a full line with line break