I am not an expert in this, but the code code below just prints message "Waiting for connection.....", and doesn´t print other messages. Why? There is no exception and the thread is running, but after calling accept() method, it doesn´t continue.
public static void main(String[] args) {
try {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(0);//0 any free port
} catch (IOException e) {
System.err.println("Could not listen on port: xxx.");
System.exit(1);
}
Socket clientSocket = null;
System.out.println("Waiting for connection.....");
// try {
clientSocket = serverSocket.accept();
/* } catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}*/
//And now there is no output, "Waiting for connection....." is the last one
System.out.println("Connection successful");
System.out.println("Waiting for input.....");
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
System.out.println("Server: " + inputLine);
out.println(inputLine);
if (inputLine.equals("Bye.")) {
break;
}
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
} catch (IOException ex) {
Logger.getLogger(Sockets.class.getName()).log(Level.SEVERE, null, ex);
}
}
The code works for me, provided I updated the code to tell me port to connect my client to. Try changing the waiting message to:
System.out.println("Waiting for connection on port " + serverSocket.getLocalPort() + ".....");
and then connecting to that port using telnet:
telnet localhost <port number>
I got it echoing my input back just fine.
You could pass in the desired port as a command line parameter, rather than simply picking an arbitrary one.
Related
I'm trying to make a TCP listener on java. The software should act like "Hercules" or SocketTest. Problem is, it's not recieving any connections from other computers or devices. It does connect to Hercules or SocketTest but not to my program.
public class Server3 {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = null;
try {
System.out.println(InetAddress.getLocalHost());
serverSocket = new ServerSocket(7165,0,InetAddress.getLocalHost());
} catch (IOException e) {
System.err.println("Could not listen on port: 7165.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
System.out.println("Client connected!");
System.out.println(clientSocket.getRemoteSocketAddress()+" connected\n");
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
clientSocket.setSoTimeout(1000);
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
String inputLine ;
boolean connected = true;
while (connected)
{
try {
inputLine = in.readLine();
System.out.println("Client said : "+inputLine);
if (inputLine == null)
{
System.out.println("Client Disconnected!");
connected = false;
}
}
catch(java.net.SocketTimeoutException e)
{
System.out.println("Timed out trying to read from socket");
}
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
I also used ServerSocket socket = new ServerSocket(port) but no results.
Is there any configurations to do more than just port ? Is it even possible to make this?
I'm trying to make a basic client <-> server connection in Java. When trying to write to the server, the client sends the details correctly, and the server stalls on reading it until the client output stream is closed. Though, once the output stream is closed it apparently closes the socket, and due to that the server can't reply to the client. Here's the main snippet of code that handles this interaction.
Client:
private void sendCmd(String cmd) {
String infoToSend = cmd;
try {
socket = new Socket(hostname, port);
System.out.println("Trying to send: " + com.sun.org.apache.xml.internal.security.utils.Base64.encode(infoToSend.getBytes()));
out = new DataOutputStream(socket.getOutputStream());
out.writeBytes(com.sun.org.apache.xml.internal.security.utils.Base64.encode(infoToSend.getBytes()));
out.flush();
System.out.println("Socket is flushed");
System.out.println("Waiting for Data");
InputStream is = socket.getInputStream();
System.out.println("Trying to get data");
BufferedReader input = new BufferedReader(
new InputStreamReader(is)
);
String line;
while((line = input.readLine()) != null) {
System.out.println(line);
}
socket.close();
} catch (IOException e) { e.printStackTrace(); }
}
Server:
public void run() {
System.out.println("Got Connection");
try {
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new DataOutputStream(socket.getOutputStream());
String response;
System.out.println("Response:");
String decode = "";
while ((response = in.readLine()) != null) {
try {
decode = new String(Base64.decode(response));
} catch (Base64DecodingException e) {
e.printStackTrace();
}
}
System.out.println("Decoded: " + decode);
out.writeBytes("We got your message!");
out.flush();
out.close();
} catch (IOException e) { System.out.println("Fail"); e.printStackTrace(); }
Would anyone be able to guide me on how to fix this error. Sorry if it's super easy and I'm just unable to see it.
Sending
socket.shutdownOutput();
solved the issue.
In my client-server application, the client sends message to Server and the Server should display the message. But in my case, the client is only able to send but the server can't achieve it.
I have tried with different port numbers (i.e. 8080, 8000, 4444 etc). It seems that the socket can set up the connection, but I really don't know why the server can't read the input from client.
This is my complete project (I have ignored the main classes for both application here, because I have nothing more than just calling the methods):
EchoServer.java:
package client.server;
import java.io.*;
import java.net.*;
public class EchoServer {
public EchoServer() {
}
public void establish() {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(8080);
} catch (IOException e) {
System.out.println("Could not listen on port: 1234");
System.exit(-1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.out.println("Accept failed: 1234");
System.exit(-1);
}
PrintWriter out = null;
BufferedReader in = null;
try {
out = new PrintWriter(
clientSocket.getOutputStream(), true);
in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
} catch (IOException ioe) {
System.out.println("Failed in creating streams");
System.exit(-1);
}
String inputLine, outputLine;
try {
while ((inputLine = in.readLine()) != null) {
out.println(inputLine);
if (inputLine.equals("Bye.")) {
break;
}
}
} catch (IOException ioe) {
System.out.println("Failed in reading, writing");
System.exit(-1);
}
try {
clientSocket.close();
serverSocket.close();
} catch (IOException e) {
System.out.println("Could not close");
System.exit(-1);
}
}
}
EchoClient.java:
package server.client;
import java.io.*;
import java.net.*;
public class EchoClient {
public EchoClient() {
}
public void establish() {
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try {
//echoSocket = new Socket(InetAddress.getLocalHost(), 1234);
echoSocket = new Socket(InetAddress.getLocalHost(), 8080);
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;
try {
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
if (userInput.equals("Bye.")) {
break;
}
System.out.println("echo: " + in.readLine());
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
} catch (IOException ioe) {
System.out.println("Failed");
System.exit(
-1);
}
}
}
Your server doesn't write the incoming text to the console but only back to the client which doesn't handle incoming text from the server yet.
(out isn't System.out but Socket.out!)
In your server you are listening with readLine() in whileloop
while ((inputLine = in.readLine()) != null) {
System.out.println("inputLine "+inputLine);
which is nothing but the inputstream from client. The above SOP will print the message from client. Try to flush your streams because it won't print until your buffer is full.
Code seems to be fine. If you write some thing on PrintWriter at both server & client ends, you will get output.
Add below code in server: ( After creating Socket with accept() API)
out.println("Hello from Server");
Add below code in client ( After creating Socket)
out.println("Hello from client");
Other suggestions:
1) Create a thread once you accept a Socket Connection at server and that thread should handle all IO processing
2) You can create thread at client end too after creating Socket with Server. The new thread should handle all IO processing
This may be a stupid question, but here goes.
Im writing this chat program, where there is a server, and clients that can connect to it. I want to implement private messaging into the program, but I don't know how to get the clients to directly connect to eachother. For the server, I used a ServerSocket, which runs on a single port. To get that to work, I needed to forward a port to the server. Is there a way to get the clients to wait for connections, without forwarding a port to them?
Thanks
The whole point of TCP/IP is that a single client connects to a predefined port on a server. So yes, you'll also need to have a ServerSocket on the client that's going to accept the direct connection. You'll almost always run into trouble with port forwarding and the like, which is why UPnP was invented one day.
What you are trying to do is 'peer to peer' connectivity, aka P2P, which is always, by its very definition, plagued by firewalling problems. As such it's usually, especially for a chat, easier to use the central server as 'switchboard' server and relay the private messages as well.
I've written not long time ago a template for multiple client - server application, that might help you to solve your problem. The rest of your question was already answerd by #Niels, I think ;)
import java.net.*;
import java.io.*;
class ServeConnection extends Thread {
private Socket socket = null;
private BufferedReader in = null;
private PrintWriter out = null;
public ServeConnection(Socket s) throws IOException {
// init connection with client
socket = s;
try {
in = new BufferedReader(new InputStreamReader(
this.socket.getInputStream()));
out = new PrintWriter(this.socket.getOutputStream(), true);
} catch (IOException e) {
System.err.println("Couldn't get I/O.");
System.exit(1);
}
start();
}
public void run() {
System.out.println("client accepted from: " + socket.getInetAddress()
+ ":" + socket.getPort());
// get commands from client, until is he communicating or until no error
// occurs
String inputLine, outputLine;
try {
while ((inputLine = in.readLine()) != null) {
System.out.println("request: " + inputLine);
outputLine = inputLine;
out.println("I've recived "+outputLine);
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("server ending");
out.close();
try {
in.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
class Server {
public static void svr_main(int port) throws IOException {
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(port);
} catch (IOException e) {
System.err.println("Could not listen on port: " + port);
System.exit(1);
}
System.out.println("Server ready");
try {
while (true) {
Socket socket = serverSocket.accept();
try {
new ServeConnection(socket);
} catch (IOException e) {
System.err.println("IO Exception");
}
}
} finally {
serverSocket.close();
}
}
}
class Client {
static Socket echoSocket = null;
static PrintWriter out = null;
static BufferedReader in = null;
public static void cli_main(int port, String servername) throws
IOException {
try {
echoSocket = new Socket(servername, port);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(
echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Don't know about host: " + servername);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for " + servername);
System.exit(1);
}
System.out.println("Client ready!");
while (true) {
inputLine = (in.readLine().toString());
if (inputLine == null) {
System.out.println("Client closing!");
break;
}
// get the input and tokenize it
String[] tokens = inputLine.split(" ");
}
out.close();
in.close();
echoSocket.close();
System.out.println("Client closing");
}
}
public class MyClientServerSnippet{
public static void main(String[] args) throws IOException {
if (args.length == 0) {
System.err.println("Client: java snippet.MyClientServerSnippet<hostname> <port>");
System.err.println("Server: java snippet.MyClientServerSnippet<port>");
System.exit(1);
}
else if (args.length > 1) {
System.out.println("Starting client...\n");
Client client = new Client();
client.cli_main(3049, "127.0.0.1");
} else {
System.out.println("Starting server...\n");
Server server = new Server();
server.svr_main(3049);
}
}
}
Hello guys I am trying to do an echo Server by java but it is nnot working .. .I don't know why .. but it seems like the server is waiting the client and the client is waiting the server ... so they can't deliver the infromation to each other ..
here is the code
for the Server
ServerSocket server = null;
try {
server = new ServerSocket(3333);
System.out.println("Listening on 3333");
} catch (IOException ex) {
System.out.println("Error can't connect to 3333");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = server.accept();
} catch (IOException ex) {
System.out.println("Accept fail");
System.exit(1);
}
PrintWriter out = null;
try {
out = new PrintWriter(clientSocket.getOutputStream());
} catch (IOException ex) {
Logger.getLogger(JavaApplication20.class.getName()).log(Level.SEVERE, null, ex);
}
BufferedReader br = null;
try {
br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
} catch (IOException ex) {
Logger.getLogger(JavaApplication20.class.getName()).log(Level.SEVERE, null, ex);
}
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String inputLine, outputLine;
while(!(inputLine=br.readLine()).equals("bye"))
{
out.print("echo: " + inputLine);
}
out.close();
br.close();
clientSocket.close();
server.close();
System.out.println("Server Exited");
and here is the code for the client
Socket client = null;
try {
client = new Socket("localhost", 3333);
System.out.println("Connected on 3333");
} catch (UnknownHostException ex) {
System.out.println("Couldn't connect to the server");
System.exit(1);
} catch (IOException ex) {
Logger.getLogger(KnockKnockClient.class.getName()).log(Level.SEVERE, null, ex);
}
PrintWriter out = null;
BufferedReader in = null;
BufferedReader stdIn = null;
try {
out = new PrintWriter(client.getOutputStream(), true);
} catch (IOException ex) {
Logger.getLogger(KnockKnockClient.class.getName()).log(Level.SEVERE, null, ex);
}
try {
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
} catch (IOException ex) {
Logger.getLogger(KnockKnockClient.class.getName()).log(Level.SEVERE, null, ex);
}
stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer, fromUser;
while((fromUser=stdIn.readLine())!=null)
{
System.out.println("From user: "+ fromUser);
out.print(fromUser);
fromServer=in.readLine();
System.out.println(fromServer);
}
out.close();
stdIn.close();
in.close();
client.close();
System.out.println("client Exited");
Any Help with that ??
You're sending some string from the client ("Hello" for example), and you're trying to read it with readLine() on the server (and vice versa). readLine() will only return once it finds an EOL character, or once the input stream is closed.
Since the client doesn't send any EOL char, the server waits indefinitely, and the client also because it waits for the answer from the server.
Send "Hello\n", and it will work better.
After out.print(fromUser); use out.flush() in your client and server. flush will make sure it will right to the socket.
while((fromUser=stdIn.readLine())!=null)
{
System.out.println("From user: "+ fromUser);
out.print(fromUser);
out.flush();
fromServer=in.readLine();
System.out.println(fromServer);
}
out.close();
stdIn.close();
in.close();
client.close();
Regarding flush, Extracted from java doc.
Flushes the stream. If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.
If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written to the stream are passed to the operating system for writing; it does not guarantee that they are actually written to a physical device such as a disk drive.