Server Socket Help!
Hello!
I have a problem regarding server socket, i wrote a simple server socket program which would accept a socket then write through the DataOutputStream, using writeByte and read through the DataInputStream using readUnsignedByte.
My server socket is a java program, and the client was created using other language (which i do not know what language but it is already existing..).
My concern is that when I try to listen (in the server side), i would accept the socket, and the connection would now be established. BUT, whenever i would close my streams (input and output stream), the client socket I accepted and the ACTUAL server socket, the client is still connected. That's why whenever i would open my Server Socket, i would no longer receive any socket.. why is it like that..?
Can anyone help me..? Please do so.. I would appreciate your immediate reply..
Thanks a lot!
Ron
HI,
What you need in the client app is for it to listen for a CLOSE message like this (java code but the logic is there)
String fromServer ;
while(( fromServer = in.readLine()) != null )
System.out.println( "Server: " + fromServer ) ;
if( fromServer.equals("Closing down")) //checks all the time for the CLOSE signal !
break ;
// other stuff
out.close() ; // close the client end of the socket on the signal !
in.close() ;
You say the client app is already written. Well look in the specs and see what the CLOSE signal is.
There MUST be one or the client app doesn't work.
Hope that helps,
Similar Messages
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FU Ant task failure: java.util.concurrent.ExecutionException: could not close client/server socket
We sometimes see this failure intermitently when using the FlexUnit Ant task to run tests in a CI environment. The Ant task throws this exception:
java.util.concurrent.ExecutionException: could not close client/server socket
I have seen this for a while now, and still see it with the latest 4.1 RC versions.
Here is the console output seen along with the above exception:
FlexUnit player target: flash
Validating task attributes ...
Generating default values ...
Using default working dir [C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\Source\Flex]
Using the following settings for the test run:
FLEX_HOME: [C:\dev\vert-d3flxcmn32\302100.41.0.20110323122739_d3flxcmn32]
haltonfailure: [false]
headless: [false]
display: [99]
localTrusted: [true]
player: [flash]
port: [1024]
swf: [C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\build\commons.formatter.tests.unit.sw f]
timeout: [1800000ms]
toDir: [C:\DJTE\commons.formatter_swc\d3flxcmn32\reports\xml]
Setting up server process ...
Entry [C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\build] already available in local trust file at [C:\Users\user\AppData\Roaming\Macromedia\Flash Player\#Security\FlashPlayerTrust\flexUnit.cfg].
Executing 'rundll32' with arguments:
'url.dll,FileProtocolHandler'
'C:\DJTE\commons.formatter_swc\d3flxcmn32\extracted\build\commons.formatter.tests.unit.swf '
The ' characters around the executable and arguments are
not part of the command.
Starting server ...
Opening server socket on port [1024].
Waiting for client connection ...
Client connected.
Setting inbound buffer size to [262144] bytes.
Receiving data ...
Sending acknowledgement to player to start sending test data ...
Stopping server ...
End of test data reached, sending acknowledgement to player ...
When the problem occurs, it is not always during the running of any particular test (that I am aware of). Recent runs where this failure was seen had the following number of tests executed (note: the total number that should be run is 45677): 18021, 18, 229.
Here is a "good" run when the problem does not occur:
Setting inbound buffer size to [262144] bytes.
Receiving data ...
Sending acknowledgement to player to start sending test data ...
Stopping server ...
End of test data reached, sending acknowledgement to player ...
Closing client connection ...
Closing server on port [1024] ...
Analyzing reports ...
Suite: com.formatters.help.TestGeographicSiteUrls
Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.008 sec
Suite: com.formatters.functionalUnitTest.testCases.TestNumericUDF
Tests run: 13, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.071 sec
Results :
Tests run: 45,677, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 201.186 sec
Has anyone else ran across this problem?
Thanks,
TrevorI am not sure if this information will help everyone, but here goes...
For us, these problems with FlexUnit tests crashing the Flash Player appear to be related to couple of factors. Recently, we moved up from Flex 3.2 to Flex 4.1 as our development baseline. Many people complained that their development environment (Flash Builder, etc.) was much more unstable. Apparently, 4.1 produces SWFs that require more memory to run than 3.2 does? Anyway, we still had Flash Player 10.1 as our runtime baseline. Apparently, that version of the player was not as capable of running larger FlexUnit test SWFs, and would crash (as I posted months earlier). I upgraded to the latest 10.3 standalone player versions, and the crashes have now ceased. It would be nice to know exactly what was causing the crashes, but memory management (or lack of) is my best guess.
So, if you are seeing these issues, try upgrading to the latest Flash Player version.
Regards,
Trevor -
How to detect client socket shutdowns in server socket
Hi,
Hoping to get some help with this. I am writing this program that implements a socket server that accepts a single client socket (from a third-party system). This server receives messages from another program and writes them to the client socket. It does not read anything back from the client. However, the client (which I have no control over) disconnects and reconnects to my server at random intervals. My issue is I cannot detect when the client has disconnected (normally or due to a network failure), hence am unable to accept a fresh connection from the client. Here's my code for the server.
ServerSocket serverSocket = null;
Socket clientSocket = null;
PrintWriter out = null;
BufferedReader in = null;
try{
if (serverSocket == null){
serverSocket = new ServerSocket(4511);
clientSocket = serverSocket.accept();
System.out.println("Accepted client request ... ");
out = new PrintWriter(clientSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
System.out.println("Input / Output streams intialized ...");
while (true){
System.out.println("Is Client Socket Closed : " + clientSocket.isClosed());
System.out.println("Is Client Socket Connected : " + clientSocket.isConnected());
System.out.println("Is Client Socket Bound : " + clientSocket.isBound());
System.out.println("Is Client Socket Input Shutdown : " + clientSocket.isInputShutdown());
System.out.println("Is Client Socket Output Shutdown : " + clientSocket.isOutputShutdown());
System.out.println("Is Server Socket Bound : " + serverSocket.isBound());
System.out.println("Is Server Socket Closed : " + serverSocket.isClosed());
messageQueue = new MessageQueue(messageQueueDir+"/"+messageQueueFile);
//get Message from Queue Head (also removes it)
message = getQueueMessage(messageQueue);
//format and send to Third Party System
if (message != null){
out.println(formatMessage(message));
System.out.println("Sent to Client... ");
//sleep
System.out.println("Going to sleep 5 sec");
Thread.sleep(5000);
System.out.println("Wake up ...");
}catch(IOException ioe){
System.out.println("initSocketServer::IOException : " + ioe.getMessage());
}catch(Exception e){
System.out.println("initSocketServer::Exception : " + e.getMessage());
}I never use the client's inputstream to read, although I have declared it here. After the client is connected (it enters the while loop), it prints the following. These values stay the same even after the client disconnects.
Is Client Socket Closed : false
Is Client Socket Connected : true
Is Client Socket Bound : true
Is Client Socket Input Shutdown : false
Is Client Socket Output Shutdown : false
Is Server Socket Bound : true
Is Server Socket Closed : false
So, basically I am looking for a condition that detects that the client is no longer connected, so that I can bring serverSocket.accept() and in and out initializations within the while loop.
Appreciate much, thanks.Crossposted and answered.
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Can i run UDP client and UDP server socket program in the same pc ?
hi all.
when i execute my UDP client socket program and UDP server socket program in the same pc ,
It's will shown the error msg :
"Address already in use: Cannot bind"
but if i run UDP client socket program in the remote pc and UDP server socket program run in local pc , it's will success.
anybody know what's going on ?
any help will be appreciated !bobby92 wrote:
i have use a specified port for UDP server side , and for client define the server port "DatagramSocket clientSocket= new DatagramSocket(Server_PORT);"Why? The port you provide here is not the target port. It's the local port you listen on. That's only necessary when you want other hosts to connect to you (i.e. when you're acting as a server).
The server should be using that constructor, the client should not be specifying a port.
so when i start the udp server code to listen in local pc , then when i start UDP client code in local pc ,i will get the error "Address already in use: Cannot bind"Because your client tries to bind to the same port that the server already bound to. -
Problems Reading SSL server socket data stream using readByte()
Hi I'm trying to read an SSL server socket stream using readByte(). I need to use readByte() because my program acts an LDAP proxy (receives LDAP messages from an LDAP client then passes them onto an actual LDAP server. It works fine with normal LDAP data streams but once an SSL data stream is introduced, readByte just hangs! Here is my code.....
help!!! anyone?... anyone?
1. SSL Socket is first read into " InputStream input"
public void run()
Authorization auth = new Authorization();
try {
InputStream input = client.getInputStream();
while (true)
{ StandLdapCommand command;
try
command = new StandLdapCommand(input);
Authorization t = command.get_auth();
if (t != null )
auth = t;
catch( SocketException e )
{ // If socket error, drop the connection
Message.Info( "Client connection closed: " + e );
close( e );
break;
catch( EOFException e )
{ // If socket error, drop the connection
Message.Info( "Client connection close: " + e );
close( e );
break;
catch( Exception e )
//Way too many of these to trace them!
Message.Error( "Command not processed due to exception");
close( e );
break;
//continue;
processor.processBefore(auth, command);
try
Thread.sleep(40); //yield to other threads
catch(InterruptedException ie) {}
catch (Exception e)
close(e);
2 Then data is sent to an intermediate function
from this statement in the function above: command = new StandLdapCommand(input);
public StandLdapCommand(InputStream in) throws IOException
message = LDAPMessage.receive(in);
analyze();
Then finally, the read function where it hangs at "int tag = (int)din.readByte(); "
public static LDAPMessage receive(InputStream is) throws IOException
* LDAP Message Format =
* 1. LBER_SEQUENCE -- 1 byte
* 2. Length -- variable length = 3 + 4 + 5 ....
* 3. ID -- variable length
* 4. LDAP_REQ_msg -- 1 byte
* 5. Message specific structure -- variable length
DataInputStream din = new DataInputStream(is);
int tag = public static LDAPMessage receive(InputStream is) throws IOException
* LDAP Message Format =
* 1. LBER_SEQUENCE -- 1 byte
* 2. Length -- variable length = 3 + 4 + 5 ....
* 3. ID -- variable length
* 4. LDAP_REQ_msg -- 1 byte
* 5. Message specific structure -- variable length
DataInputStream din = new DataInputStream(is);
int tag = (int)din.readByte(); // sequence tag// sequence tag
...I suspect you are actually getting an Exception and not tracing the cause properly and then doing a sleep and then getting another Exception. Never ever catch an exception without tracing what it actually is somewhere.
Also I don't know what the sleep is supposed to be for. You will block in readByte() until something comes in, and that should be enough yielding for anybody. The sleep is just literally a waste of time. -
Server Socket does not read data input stream
Hi all,
I am very newbie to Java Network programming with sockets and multi-threading.
But I am obliged to develop a chat system written in Applets which can be placed on the website and used by visitors who come to my website.
In order to understand this, I have tested a basic web chat program I downloaded from the Internet which use sockets and multi-threadings. The program work fine, no bugs at all at both compilation and run time. I noticed that all three streams for Client side (i.e. first one is input stream used receiving data from User; the second one is socket input stream used for receiving data from Server socket, and the third is socket output stream used for writing data to server socket) were established. And the same, two socket streams (input & output) for Server side were also connected when running program giving right port number and IP address of the server.
The problem is both server and client sockets do not read data using the following stream classes:
1. DataStreamInput: I use input.readUTF() method
2. or BufferedReader: I use input.readLine() method
The example of the codes are below:
private BufferedReader input = null;
private PrintWriter output = null;
private Socket socket = null;
public void open() throws IOException
{ input = new BufferedReader(new
InputStreamReader(socket.getInputStream()));
System.out.println("Server socket input stream was created, and");
output = new PrintWriter(socket.getOutputStream());
System.out.println("Server socket output stream was created");
public void run()
{ System.out.println("Server Thread " + clientPort + " running.");
while (true)
{ try
System.out.println("Server is reading data from Client, wait...");
String fromClient = input.readLine();
System.out.println("Server received a message on " + clientPort + ".");
catch(IOException ioe)
{ System.out.println(clientPort + " ERROR reading: " + ioe.getMessage());
server.remove(clientPort);
stop();
The problem is at the line: String fromClient = input.readLine(); in the run() method? What is wrong with the codes above?
Note: I also try to use original codes which use readUTF() method in DataStreamInput class instead using readLine() in BufferedReader. Both methods dont read data from inputstream socket?
I very appreciate any help/advice from experienced developers.
Best regardsHi,
Yes. The readLine() method hangs! After the test, the execuation of the program is stopped at the line of readLine() method; it does not pass it?
There is no problem with writing to Server socket. After the test, the program pass through flush() method. Here is the code for writing to sever socket within ChatClient (client side socket) class:
private BufferedReader input = null;
private PrintWriter output = null;
public ChatClient(String serverName, int serverPort)
{ System.out.println("Establishing connection. Please wait ...");
try
{ socket = new Socket(serverName, serverPort);
System.out.println("Connected: " + socket);
start();
catch(UnknownHostException uhe)
{ System.out.println("Host unknown: " + uhe.getMessage()); }
catch(IOException ioe)
{ System.out.println("Unexpected exception: " + ioe.getMessage()); }
public void start() throws IOException
{ input = new BufferedReader (new
InputStreamReader(System.in));
System.out.println("Client User input stream was created,");
output = new PrintWriter(socket.getOutputStream());
System.out.println("Client Socket output stream was established, and");
if (thread == null)
{ client = new ChatClientThread(this, socket);
thread = new Thread(this);
thread.start();
public void run()
while (thread != null) {
String fromUser;
try{
while((fromUser = input.readLine())!= null)
System.out.println("Client wasreading a data from User, and");
output.println(fromUser);
output.flush();
System.out.println("Client has written a data to Server");
catch(IOException ioe)
{ System.out.println("Sending to server error: " + ioe.getMessage());
stop();
etc.
Here is a piece of codes for reading data from the Client Socket in the ChatServer Class (Server Side socket):
public void run()
{ System.out.println("Server Thread " + clientPort + " running.");
while (true)
{ try
{ //server.handle(clientPort, input.readLine());
System.out.println("Server is reading data from Client, wait...");
String fromUser = input.readLine();
//while((fromUser = input.readLine()) != null)
System.out.println("Server received a message on " + clientPort + ".");
catch(IOException ioe)
{ System.out.println(clientPort + " ERROR reading: " + ioe.getMessage());
server.remove(clientPort);
stop();
etc. Please advice why the readLine() method hangs; does not read data from the input stream received from the CLIENT? -
Problem in server program: HELP!!!!
I just tried to introduce methods in my server program (TCPServer.java). the methods are
run_server() : for creating server socket object
[b[accept() [/b]: for Listening to a connection, made to the socket and accepting it.
getstreams() : initializing the streams
b]recieve_n_process() : receiving client input and processing it
send_response(): sending response back to client.
But now I am getting runtime exception
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>javac TCPServer.java
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>java TCPServer
Exception in thread "main" java.lang.NullPointerException
at TCPServer.accept(TCPServer.java:19)
at TCPServer.main(TCPServer.java:58)
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>
I know I might have made some silly mistake somewhere, please help me to detect it.
here is my code TCPServer.java
import java.io.*;
import java.net.*;
class TCPServer {
private ServerSocket welcomeSocket;
private Socket connectionSocket;
private ObjectInputStream Client_input;
private ObjectOutputStream Client_output;
private String clientSentence;
private String capitalizedSentence;
private void run_server() throws Exception
ServerSocket welcomeSocket = new ServerSocket(80);
private void accept() throws Exception
{connectionSocket = welcomeSocket.accept(); }
private void getstreams() throws IOException
Client_output = new ObjectOutputStream(connectionSocket.getOutputStream());
Client_output.flush();
Client_input = new ObjectInputStream(connectionSocket.getInputStream());
private void recieve_n_process() throws Exception
clientSentence = (String ) Client_input.readObject();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
private void send_response() throws IOException
Client_output.writeObject(capitalizedSentence);
public static void main(String argv[]) throws Exception
TCPServer server = new TCPServer();
try{
server.run_server();
while(true) {
server.accept();
server.getstreams() ;
server.recieve_n_process();
server.send_response();
} catch(EOFException eofException) {}
catch (IOException ioException) {}
}It was working fine before I introduced these methods. Earlier it was like this
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(80);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
ObjectInputStream inFromClient = new ObjectInputStream(connectionSocket.getInputStream());
ObjectOutputStream outToClient =
new ObjectOutputStream(connectionSocket.getOutputStream());
clientSentence = (String ) inFromClient.readObject();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeObject(capitalizedSentence);hello every one,
i got it where is the problem. I had declared the object of ServerSocket class locally in run_server(). It had to be declared globally though.
private void run_server() throws Exception
ServerSocket welcomeSocket = new ServerSocket(80);
this one works out
private void run_server() throws Exception
welcomeSocket = new ServerSocket(80);
} -
Problem trying to read an SSL server socket stream using readByte().
Hi I'm trying to read an SSL server socket stream using readByte(). I need to use readByte() because my program acts an LDAP proxy (receives LDAP messages from an LDAP client then passes them onto an actual LDAP server. It works fine with normal LDAP data streams but once an SSL data stream is introduced, readByte just hangs! Here is my code.....
help!!! anyone?... anyone?
1. SSL Socket is first read into " InputStream input"
public void run()
Authorization auth = new Authorization();
try {
InputStream input = client.getInputStream();
while (true)
{ StandLdapCommand command;
try
command = new StandLdapCommand(input);
Authorization t = command.get_auth();
if (t != null )
auth = t;
catch( SocketException e )
{ // If socket error, drop the connection
Message.Info( "Client connection closed: " + e );
close( e );
break;
catch( EOFException e )
{ // If socket error, drop the connection
Message.Info( "Client connection close: " + e );
close( e );
break;
catch( Exception e )
//Way too many of these to trace them!
Message.Error( "Command not processed due to exception");
close( e );
break;
//continue;
processor.processBefore(auth, command);
try
Thread.sleep(40); //yield to other threads
catch(InterruptedException ie) {}
catch (Exception e)
close(e);
2 Then data is sent to an intermediate function
from this statement in the function above: command = new StandLdapCommand(input);
public StandLdapCommand(InputStream in) throws IOException
message = LDAPMessage.receive(in);
analyze();
Then finally, the read function where it hangs at "int tag = (int)din.readByte(); "
public static LDAPMessage receive(InputStream is) throws IOException
* LDAP Message Format =
* 1. LBER_SEQUENCE -- 1 byte
* 2. Length -- variable length = 3 + 4 + 5 ....
* 3. ID -- variable length
* 4. LDAP_REQ_msg -- 1 byte
* 5. Message specific structure -- variable length
DataInputStream din = new DataInputStream(is);
int tag = (int)din.readByte(); // sequence tag// sequence tagI suspect you are actually getting an Exception and not tracing the cause properly and then doing a sleep and then getting another Exception. Never ever catch an exception without tracing what it actually is somewhere.
Also I don't know what the sleep is supposed to be for. You will block in readByte() until something comes in, and that should be enough yielding for anybody. The sleep is just literally a waste of time. -
I have written a java program, that is running on 2 PCs. I would like to display the outcomes of the program on one of those PCs. I believe I need a server socket to do this, but I am not really sure. Can someone help me? Thanks!
Yes, java applications can communicate using sockets.
Assuming your 2 PCs can "ping" each other.
A ServerSocket listens for connections on a port and creates a new Socket when a client connects.
What are you having problems with? -
Server Socket Leaks on stopping Java Processes
I have a strange problem on Windows 2000 Advanced Server with JDK1.5.10. Our application runs on a Tomcat 5.5.12 and is opening 2 server sockets along with Tomcat's own 8080 port. Also we deployed a stand alone application that also opens a server socket. Whenever we stop Tomcat service or our Application service (Windows services) these server sockets are not getting closed. If we use "netstat" to check if any sockets are still open it is NOT showing any sockets.
But when we use "netstat -a" command it is showing entries like
TCP 10.40.1.162:8080 10.40.1.162:0 LISTENING
TCP 10.40.1.162:22222 10.40.1.162:0 LISTENING
TCP 10.40.1.162:33334 10.40.1.162:0 LISTENINGHere 8080 (tomcat), 22222, 33334 are the ports on which the server sockets are opened earlier. We check in Task Manager but there is no java process running. If we try to restart the same java process it is throwing JVM_Bind exception. If we reboot the box the we are able to restart the services. Similar behaviour we observed sometimes on Linux also. I guess some settings in the OS we need to tweak to fix this issue. Can somebody please help me what are those settings for Windows and Linux platforms which reclaims unused server sockets faster??The state is LISTENING not TIME_WAIT. There is a cleanly closure of sockets provided in the code. It happens to Tomcat's own ports also. If you telnet to these sockets from another box, it is connecting and staying instead of "Connection Failed" error. But in Task Manager or "Services.msc" Console no service or process running! One more observation is that there is heavy load of threads and a huge number of clients socktets were interacting with these sockets just before shutdown.
-
Problems reading an SSL server socket stream using readByte()
Hi I'm trying to read an SSL server socket stream using readByte(). I need to use readByte() because my program acts an LDAP proxy (receives LDAP messages from an LDAP client then passes them onto an actual LDAP server. It works fine with normal LDAP data streams but once an SSL data stream is introduced, readByte just hangs! Here is my code.....
help!!! anyone?... anyone?
1. SSL Socket is first read into " InputStream input"
public void run()
Authorization auth = new Authorization();
try {
InputStream input = client.getInputStream();
while (true)
{ StandLdapCommand command;
try
command = new StandLdapCommand(input);
Authorization t = command.get_auth();
if (t != null )
auth = t;
catch( SocketException e )
{ // If socket error, drop the connection
Message.Info( "Client connection closed: " + e );
close( e );
break;
catch( EOFException e )
{ // If socket error, drop the connection
Message.Info( "Client connection close: " + e );
close( e );
break;
catch( Exception e )
//Way too many of these to trace them!
Message.Error( "Command not processed due to exception");
close( e );
break;
//continue;
processor.processBefore(auth, command);
try
Thread.sleep(40); //yield to other threads
catch(InterruptedException ie) {}
catch (Exception e)
close(e);
2 Then data is sent to an intermediate function
from this statement in the function above: command = new StandLdapCommand(input);
public StandLdapCommand(InputStream in) throws IOException
message = LDAPMessage.receive(in);
analyze();
Then finally, the read function where it hangs at "int tag = (int)din.readByte(); "
public static LDAPMessage receive(InputStream is) throws IOException
* LDAP Message Format =
* 1. LBER_SEQUENCE -- 1 byte
* 2. Length -- variable length = 3 + 4 + 5 ....
* 3. ID -- variable length
* 4. LDAP_REQ_msg -- 1 byte
* 5. Message specific structure -- variable length
DataInputStream din = new DataInputStream(is);
int tag = (int)din.readByte(); // sequence tag// sequence tagI suspect you are actually getting an Exception and not tracing the cause properly and then doing a sleep and then getting another Exception. Never ever catch an exception without tracing what it actually is somewhere.
Also I don't know what the sleep is supposed to be for. You will block in readByte() until something comes in, and that should be enough yielding for anybody. The sleep is just literally a waste of time. -
Hi,
As the name of the forum suggests I am very new to this whole thing.
I am trying to write a client/server socket program that can encrypt and decrypt and has a GUI, can't use JCE or SSL or any built in encryption tools.
I have the code for everything cept the encryption part.
Any help, greatly appreciated,tnks a million but how do i incorporate that into the following client and server code:
here's the client code:
import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.net.*;
class SocketClient extends JFrame
implements ActionListener {
JLabel text, clicked;
JButton button;
JPanel panel;
JTextField textField;
Socket socket = null;
PrintWriter out = null;
BufferedReader in = null;
SocketClient(){ //Begin Constructor
text = new JLabel("Text to send over socket:");
textField = new JTextField(20);
button = new JButton("Click Me");
button.addActionListener(this);
panel = new JPanel();
panel.setLayout(new BorderLayout());
panel.setBackground(Color.white);
getContentPane().add(panel);
panel.add("North", text);
panel.add("Center", textField);
panel.add("South", button);
} //End Constructor
public void actionPerformed(ActionEvent event){
Object source = event.getSource();
if(source == button){
//Send data over socket
String text = textField.getText();
out.println(text);
textField.setText(new String(""));
//Receive text from server
try{
String line = in.readLine();
System.out.println("Text received :" + line);
} catch (IOException e){
System.out.println("Read failed");
System.exit(1);
public void listenSocket(){
//Create socket connection
try{
socket = new Socket("HUGHESAN", 4444);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
} catch (UnknownHostException e) {
System.out.println("Unknown host: HUGHESAN.eng");
System.exit(1);
} catch (IOException e) {
System.out.println("No I/O");
System.exit(1);
public static void main(String[] args){
SocketClient frame = new SocketClient();
frame.setTitle("Client Program");
WindowListener l = new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
frame.addWindowListener(l);
frame.pack();
frame.setVisible(true);
frame.listenSocket();
SERVER Code
import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.net.*;
class SocketServer extends JFrame
implements ActionListener {
JButton button;
JLabel label = new JLabel("Text received over socket:");
JPanel panel;
JTextArea textArea = new JTextArea();
ServerSocket server = null;
Socket client = null;
BufferedReader in = null;
PrintWriter out = null;
String line;
SocketServer(){ //Begin Constructor
button = new JButton("Click Me");
button.addActionListener(this);
panel = new JPanel();
panel.setLayout(new BorderLayout());
panel.setBackground(Color.white);
getContentPane().add(panel);
panel.add("North", label);
panel.add("Center", textArea);
panel.add("South", button);
} //End Constructor
public void actionPerformed(ActionEvent event) {
Object source = event.getSource();
if(source == button){
textArea.setText(line);
public void listenSocket(){
try{
server = new ServerSocket(4444);
} catch (IOException e) {
System.out.println("Could not listen on port 4444");
System.exit(-1);
try{
client = server.accept();
} catch (IOException e) {
System.out.println("Accept failed: 4444");
System.exit(-1);
try{
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out = new PrintWriter(client.getOutputStream(), true);
} catch (IOException e) {
System.out.println("Accept failed: 4444");
System.exit(-1);
while(true){
try{
line = in.readLine();
//Send data back to client
out.println(line);
} catch (IOException e) {
System.out.println("Read failed");
System.exit(-1);
protected void finalize(){
//Clean up
try{
in.close();
out.close();
server.close();
} catch (IOException e) {
System.out.println("Could not close.");
System.exit(-1);
public static void main(String[] args){
SocketServer frame = new SocketServer();
frame.setTitle("Server Program");
WindowListener l = new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
frame.addWindowListener(l);
frame.pack();
frame.setVisible(true);
frame.listenSocket();
Again help on this is very welcomed -
JavaMail Server: Sockets and Mail
L.S,
I'm thinking about combining code based on the Java Mail API and the Java networking tutorial (server sockets). I'm thinking I should listen to ports 25 and 110 using SMTP and POP3 protocol classes respectively.
The problem I'm running into right now is that I haven't found a way to translate incoming email messages (bytestreams) into Java Mail objects.
Can anyone point me in the right direction and help me find out how to translate bytes received at ServerSocket objects (ServerSocket(25) and ServerSocket(110)) into Java mails?Thanks, those are indeed important documents. Currently, I'm able to listen at port 25 for any incoming network transmissions. Unfortunately, when I try sending an email to the machine, the program sending it reports an error about the domain not being found (I also see nothing in my server console).
ServerSocket smtp = new ServerSocket(25);
boolean listening = true;
while (listening) {
Socket s = smtp.accept();
PrintWriter out = new PrintWriter(s.getOutputStream(),true);
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
System.out.println(in.readLine());
out.println("ok");
listening = false;
s.close();
smtp.close();According to me, the above program should at least print something to the console when another machine in my network sends an email to this machine (all@myclient). Somehow, though, I'm not getting anything... -
Hi,I am using the server socket in Java to listen on a port on a computer..
I am using the windows platform
I use ms vj++6.0
I am facing a peculiar problem.
about once in 10 messages received by my server socket,
The server socket hangs .
Hangs means it stops responding to the incoming message & so my application
is unable to take any action.
I used a port scanner & found that my server port is in a "close_wait"
state.
Can someone tell me the reason for this.
is it a problem with my server or can the client that sends the message be
also responsible for this type of an error.
Heres the code for my server
public server()
try
server = new ServerSocket(2156);
serverthread = new Thread(this);
serverthread.start();
catch(Exception e)
System.out.println("Cannot Start Thread" + e);
public synchronized void run()
try
while(true)
String line;
System.out.println("listening for the client");
fromclient = server.accept();
System.out.println("client has responded");
InputStreamReader isr = new
InputStreamReader(fromclient.getInputStream());
BufferedReader instream = new BufferedReader(isr);
PrintWriter ostream = new PrintWriter(new
BufferedOutputStream(fromclient.getOutputStream()));
System.out.println("talking to the client\n");
ostream.println("Hye Client");
ostream.println("Bye");
ostream.flush();
System.out.println("listening to the client \n");
String temp;
int count=0;
String ip="";
while((line=instream.readLine())!=null)
System.out.println(line+"\n");
if (line.equals("Bye"))
break;
if (line.equals(""))
continue;
else
System.out.println(line+"\n"); /*Print the line that has come in the
socket*/
ostream.close();
fromclient.close();
catch(Exception e)
System.out.println("Cannot listen to the client" + e);
I hope somebody can help me out .
Thanx in advance
Regards
Sanket GuptaYou don't seem to properly close the server socket any where. Here why don't you look at this skeleton. This may help you.
import java.net.*;
import java.io.*;
import java.util.*;
public class server
static boolean listen = true;
public static void main(String args[])
try
ServerSocket ss = new ServerSocket(2156);
do
new serverThread(ss.accept()).start();
while(listen);
ss.close();
catch(IOException e)
System.err.println(e.getMessage());
public static void shutdown()
listen = false;
class serverThread extends Thread
private Socket client;
private String input;
private BufferedReader in;
private PrintWriter out;
public serverThread(Socket c)
client = c;
public void run()
try
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
out = new PrintWriter(client.getOutputStream(),true);
input = in.readLine();
if(input.equals("Hello"))
out.println("How are you doing?");
else if(input.equals("shutdown!"))
server.shutdown();
else
out.println("Bad Request!");
in.close();
out.close();
client.close();
catch(IOException e)
System.err.println(e.getMessage());
} -
How come the server socket does not recieve all requests coming from Internet explorer? I am listening on PORT 5678 and I don't get all the requests from the browser, I keep getting empty requests. Any help with this would be greatly appreciated.
I figured it out myself, turns out the .available() function on the input stream is less than reliable on all platforms, especially windows XP, as it the .ready() function in the InputStreamReader class. Just posted this in case anyone had similar problems.
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