I have been trying for hours and I just can't seem to get it done. I want to send two strings from TCP client to server, and return them both capitalized. The two strings are username and password:
Client code is:
public void actionPerformed(ActionEvent e) {
final String s1 =textPane.getText(); //retrieve username
final String s2=passwordField.getText();//retrieve password
//**************************************************************************
//after we have gotten the credentials, we have to send them to the server to check in the database
Socket clientSocket = null; //create new socket
String response=null; //create what is supposed to become the server's response
String response2=null;
try {
/**
* construct the client socket, specify the IP address which is here
* localhost for the loopback device and the port number at which a
* connection needs to be initialized.
*/
clientSocket = new Socket("localhost", 6789);
// These streams are for the same purpose as in the server side //
DataOutputStream outToServer = new DataOutputStream(clientSocket
.getOutputStream());
DataOutputStream outToServer2 = new DataOutputStream(clientSocket
.getOutputStream());
BufferedReader inFromServer = new BufferedReader(
new InputStreamReader(clientSocket.getInputStream()));
// read the user's input from the console. //
// send the sentence to the server: note the need to append it with
// an endline character //
outToServer.writeBytes(s1 + '\n'); //send username
outToServer.writeBytes(s2 + '\n'); //send password
// listen on the socket and read the reply of the server //
response2=inFromServer.readLine();
response = inFromServer.readLine();
} catch (UnknownHostException ex) {// catch the exceptions //
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
System.out.println("FROM SERVER: " + response); //print the response of the server
System.out.println("FROM SERVER: " + response2);
try {
// close the socket when done //
clientSocket.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
});
Bulk of Server Code is:
while(true) {
// connection socket //
Socket connectionSocket;
try {
// accept connection on the connection socket from the welcome socket which is a server socket //
connectionSocket = welcomeSocket.accept();
// Get the input stream from the connection socket and save it in a buffer //
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
// Allocate an output stream to send data back to the client //
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
// Read the client sentence from the receive buffer //
clientSentence = inFromClient.readLine();
clientSentence2=inFromClient.readLine();
System.out.println("From user: " + clientSentence);
// capitalize the client's sentence, here the server does actions on the client's data //
capitalizedSentence = clientSentence.toUpperCase() + '\n';
capitalizedSentence2=clientSentence2.toUpperCase()+'\n';
if(clientSentence.equalsIgnoreCase("QUIT")){// close the socket if the server sends a quit message //
connectionSocket.close();
System.out.println("Connection Socket Quitting");
// Note that here the server will not exit or end up it will just close the connection with the client //
}
else outToClient.writeBytes(capitalizedSentence);// Send the capitalized sentence back to the client //
} catch (IOException ex) {
ex.printStackTrace();
}
}
What am I doing wrong? Can't one buffered reader accept two separate strings? How do I separate them later?
You haven't written back capitalizedSentence2 back to client that's why client is waiting at second readLine() as mentioned below:
response2 = inFromServer.readLine();
response = inFromServer.readLine();
put below line in your server side code in else part
outToClient.writeBytes(capitalizedSentence2);
It might solve your problem.
Related
So here's the thing, I have a basic java server that sends back to the client what ever it receives from it. The client is written in python. I'm able to make the first connection as in the server sends the client a message confirming the connection. But when I want the client to send the server something is does nothing. I'm not sure if the problem with the client not sending or the server not receiving.
Here's the code for the server:
int portNumber = Integer.parseInt(args[0]);
try (
ServerSocket serverSocket = new ServerSocket(portNumber);
Socket clientSocket = serverSocket.accept();
PrintWriter outs =
new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(clientSocket.getInputStream()));
) {
String inputLine, outputLine;
outputLine = "Hello socket, I'm server";
outs.println(outputLine);
outs.println("I' connected");
while ((inputLine = in.readLine()) != null) {
outputLine = inputLine;
outs.println(outputLine);
if (outputLine.equals("Bye."))
break;
}
} catch (IOException e) {
System.out.println("Exception caught when trying to listen on port "
+ portNumber + " or listening for a connection");
System.out.println(e.getMessage());
}
} }
and here's the client :
import socket
HOST = "localhost"
PORT = 8080
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((HOST, PORT))
print (socket.getaddrinfo(HOST,PORT))
buffer_size = 100
while True :
data = sock.recv(buffer_size)
print ('you recieved :' , data)
test = input('send here\n')
sock.sendall(bytes(test, 'utf-8'))
print ('you sent : ' , test)
In the Python client:
Your prompt contains a \n but the result from input does not? Try adding a \n to test before sending.
I created a java chat application (client and server)
Everything works fine when I'm on my LAN (using LAN IP address of the server into my client).
But when I'm using the Internet address of my server in my client, the strings are sent only when I close the output Data stream of my client (and all the strings are sent at once).
Here's a quick snap of my code (I have port forward from 6791 to 6790 in the example below),
My server (thread):
// this line is actually on my global server class, used below with theServer
ServerSocket svrSocket= new ServerSocket(6790);
//wait for incoming connection
connectionSocket = svrSocket.accept();
connectionSocket.setSoTimeout(10000);
// free the accepting port
svrSocket.close();
//create a new thread to accept future connections (creates a new svrSocket)
theServer.openNewConnection();
//create input stream
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
boolean threadRunning = true);
while (threadRunning) {
//System.out.println("thread: in the while");
try {
Thread.sleep(100);
clientSentence = inFromClient.readLine();
System.out.println(clientSentence);
}
catch...
}
My client:
InetAddress dnsName;
Socket clientSocket;
PrintWriter out;
dnsName = InetAddress.getByName("myAddress.me");
clientSocket = new Socket(dnsName.getHostAddress(), 6791);
Thread.sleep(10);
out = new PrintWriter(clientSocket.getOutputStream(), true );
int i=140;
while (i>130){
try {
out.println(Integer.toString(i));
out.flush();
Thread.sleep(200);
}
catch(Exception e) {
e.printStackTrace();
}
i--;
}
out.flush();
out.close();
clientSocket.close();
I've tried with DataOutStreams, there's nothing to do.
My server will only receive the strings when out.close() is called on client side.
Is there a reason why, over the Internet, the data stream has to be closed for data to be sent? Is there a way around this? Am I doing something wrong?
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
I have 2 classes (Client and Server) used to implement simple communication in my application. My code is shown below:
Server:
public class Server {
public static void main(String[] ar) {
int port = 1025; // just a random port. make sure you enter something between 1025 and 65535.
try {
ServerSocket ss = new ServerSocket(port); // create a server socket and bind it to the above port number.
System.out.println("Waiting for a client...");
Socket socket = ss.accept();
InputStream sin = socket.getInputStream();
OutputStream sout = socket.getOutputStream();
DataInputStream in = new DataInputStream(sin);
DataOutputStream out = new DataOutputStream(sout);
BufferedReader keyboard = new BufferedReader(new InputStreamReader(
System.in));
System.out.println("enter meter id ");
String line = null;
while (true) {
line = in.readUTF(); // wait for the client to send a line of text.
System.out.println("client send me this id number " + line);
line = keyboard.readLine();
out.writeUTF(line);
out.flush();
//line = in.readUTF();
System.out.println("Waiting for the next line...");
System.out.println();
}
} catch (Exception x) {
x.printStackTrace();
}
}
}
Client:
public class Client {
public static void main(String[] ar) {
int serverPort = 1025;
String address = "localhost";
try {
InetAddress ipAddress = InetAddress.getByName(address); // create an object that represents the above IP address.
System.out.println(" IP address " + address + " and port "
+ serverPort);
Socket socket = new Socket(ipAddress, serverPort); // create a socket with the server's IP address and server's port.
InputStream sin = socket.getInputStream();
OutputStream sout = socket.getOutputStream();
DataInputStream in = new DataInputStream(sin);
DataOutputStream out = new DataOutputStream(sout);
// Create a stream to read from the keyboard.
BufferedReader keyboard = new BufferedReader(new InputStreamReader(
System.in));
String line = null;
System.out.println("ClientConnected.");
System.out.println("enter meter id");
while (true) {
line = keyboard.readLine(); // wait for the user to type in something and press enter.
System.out.println("Sending this number to the server...");
out.writeUTF(line); // send the above line to the server.
out.flush(); // flush the stream to ensure that the data reaches the other end.
line = in.readUTF(); // wait for the server to send a line of text.
System.out
.println("The server was very polite. It sent me this : "
+ line);
System.out.println();
}
}
catch (Exception x) {
x.printStackTrace();
}
}
}
My problem is that while testing the program I do get communication between the client and server, but while debugging, with a break point on the out.flush line in Server.java, it does not go to the intended destination. This intended destination being the line line = in.readUTF(); of Client.java. Can anyone help me to solve this?
It is good practice to open the OutputStreams before the InputStreams, on your sockets, as said in this question.
This question also clarifies that.
What I suspect here is your client and server are running in two different JVM processes and java debugger cannot debug two JVM at the same time.
I'm building a Java client application which needs to send a message to a server and receive a response afterwards. I can send the message successfully, the problem is that I can't get the response because I get an IO exception ("Socked is closed") when trying to read the 'BufferedReader'.
This is my code, so far:
public class MyClass {
/**
* #param args the command line arguments
*/
#SuppressWarnings("empty-statement")
public static void main(String[] args) {
JSONObject j = new JSONObject();
try {
j.put("comando", 1);
j.put("versao", 1);
j.put("senha", "c4ca4238a0b923820dcc509a6f75849b");
j.put("usuario", "1");
j.put("deviceId", "1");
} catch (JSONException ex) {
System.out.println("JSON Exception reached");
}
String LoginString = "{comando':1,'versao':1,'senha':'c4ca4238a0b923820dcc509a6f75849b','usuario':'1','deviceId':'1'}";
try {
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = new Socket("10.1.1.12", 3333);
System.out.println("Connected to the server successfully");
PrintWriter outToServer = new PrintWriter(clientSocket.getOutputStream(),true);
outToServer.println(j.toString());
outToServer.close();
System.out.println("TO SERVER: " + j.toString());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String resposta = inFromServer.readLine();
System.out.println("FROM SERVER: " + resposta);
clientSocket.close();
} catch (UnknownHostException ex) {
System.out.println("Could not connect to the server [Unknown exception]");
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
}
I know that the socket is being closed because of the OutToServer.close() but closing the stream is the only way to send the message. How should I approach this situation?
flush() is not the case when it comes with new PrintWriter(, true).
The real problem is that you are closing the PrintWriter outToServer which wraps the underlying InputStream, again, came from the Socket.
When you close the outToServer you're closing the whole socket.
You have to use Socket#shutdownOutput().
You don't even have to close the output if you want to keep the socket's in/out channels for further communications.
flush() when you are done with any writeXXX. Those writeXXX practically don't mean you sent those bytes and characters to other side of the socket.
You may have to close the output, and output only, to signal the server that you sent all you had to send. This is really a matter of the server-side socket's desire.
final Socket socket = new Socket(...);
try {
final PrintStream out = new PrintStream(socket.getOutputStream());
// write here
out.flush(); // this is important.
socket.shutdownOutput(); // half closing
// socket is still alive
// read input here
} finally {
socket.close();
}
Try to call outToServer.flush()
That will try to flush the data from the buffer, although it still not guarantees that it will be sent.