Netcat is your friend here.

    nc -l localhost 10000 &gt; log.txt

Netcat will listen for a connection on port 10000, redirect anything received to log.txt.



Also available is TCPDump.

    sudo tcpdump -i eth0 -vvvvtttAXns 1500 &#39;port 10000&#39;

Other tools are  [Ethereal](https://www.gnutoolbox.com/tethereal-utility/) ([man page](https://man.cx/tethereal(1))) or [Wireshark](http://en.wikipedia.org/wiki/Wireshark) and it&#39;s console variant [tshark](https://www.wireshark.org/docs/man-pages/tshark.html).

In any case please be aware that you are following local and company rules. 




What&#39;s the point of the `name` attribute on an HTML form? As far as I can tell, you can&#39;t read the form name on submission or do anything else with it. Does it serve a purpose?

What&#39;s the point of HTML forms `name` attribute?

I want to clone a MongoDB collection and save it on the same server with a different name. So for example right now I have the following collections: demo1.categories, demo1.users and demo2.users.

I want to have a &quot;demo2.categories&quot; which is identical to &quot;demo1.categories&quot;. (It just has a different name.)

Clone a collection in MongoDB

Is there some easy way in linux to listen for data on network and save them to a text file?

Thank you.

Listen on a network port and save data to a text file

<p>Is there some easy way in linux to listen for data on network and save them to a text file?</p>
<p>Thank you.</p>


I want to write a Makefile which would run tests. Test are in a directory &#39;./tests&#39; and executable files to be tested are in the directory &#39;./bin&#39;.

When I run the tests, they don&#39;t see the exec files, as the directory ./bin is not in the $PATH.

When I do something like this: 

    EXPORT PATH=bin:$PATH
    make test

everything works. However I need to change the $PATH in the Makefile.

Simple Makefile content:

    test all:
        PATH=bin:${PATH}
        @echo $(PATH)
        x

It prints the path correctly, however it doesn&#39;t find the file x.


When I do this manually:

    $ export PATH=bin:$PATH
    $ x

everything is OK then.

How could I change the $PATH in the Makefile?


How I could add dir to $PATH in Makefile?

This is more about the invocation of a program, than any language or parser (though I&#39;m sure choice of parser library can depend on this). See, I&#39;ve used a lot of Linux command-line utilities. And there are some obvious patterns; &#39;-&#39; precedes a single letter for short options, multiple options that don&#39;t take arguments can be combined, &#39;--&#39; precedes long versions of options, and so on.

However, in some cases, capitalization is used to *invert* an option. So, &#39;-d&#39; might mean to run as a daemon, but &#39;-D&#39; would be to *not* run as a daemon. (Why not just omit the option if you don&#39;t want it? That&#39;s never been clear, but it&#39;s actually rather common, so I figure there must be some reason.) But in some programs, a capital is a completely unrelated option; if &#39;-d&#39; is run as daemon, &#39;-D&#39; might be to enable debug mode. Is there some kind of overarching principal behind this, and which is the best to choose? Or are we just dealing with &quot;whatever works&quot;?

There are also some commands that, in addition to (or instead of) options with arguments, just take lone arguments. cp is a good example of this; aside from a couple rarely used toggles, the last argument it receives is presumed to be the destination, and any arguments between the option list and the destination are presumed to be sources. Is there a rule of thumb when it&#39;s &quot;okay&quot; to rely on order like that, instead of using explicit option flags with arguments?

Are there standards for Linux command line switches and arguments?

I have made [Bash][1] scripts before and they all ran fine without `#!/bin/bash` at the beginning.

What&#39;s the point of putting it in? Would things be any different?

Also, how do you pronounce `#`? I know that `!` is pronounced as &quot;bang.&quot;

How is `#!` pronounced?

  [1]: http://en.wikipedia.org/wiki/Bash_%28Unix_shell%29


Why do you need to put #!/bin/bash at the beginning of a script file?

I need to learn about the ELF file layout for a project I am working on and I noticed the existence of these tools.
Why do all Linux distributions include both readelf and objdump? Do these tools complement one another? When would i prefer to use one over another?

readelf vs. objdump: why are both needed

I want to kill all processes that I get by:

    ps aux | grep my_pattern

How to do it?

This does not work:

    pkill my_pattern

 

How to kill all processes with a given partial name?

I am sending file from client to server using TCP. To mark the end of the file I like to send file size before the actual data. So I use `stat` system call to find the size of the file. This is of type `off_t`. I like to know how many bytes it occupies so that I can read it properly on the server side. It is defined in the  `&lt;sys/types.h&gt;`. But I do not understand the definition. It just defines `__off_t or _off64_t` to be `off_t`. Where to look for `__off_t`? Also is it convention that `__` is prefixed for most of the things in header files and scares me when I read header files to understand better. How to read a header file better?

    #ifndef __off_t_defined
    # ifndef __USE_FILE_OFFSET64
    typedef __off_t off_t;
    # else
    typedef __off64_t off_t;
    # endif
    # define __off_t_defined
    #endif 

Where to find the complete definition of off_t type?

How can I capture mobile phone traffic on Wireshark?

Capturing mobile phone traffic on Wireshark

I want to create an app that uses the internet and I&#39;m trying to create a function that checks if a connection is available and if it isn&#39;t, go to an activity that has a retry button and an explanation. 

Attached is my code so far, but I&#39;m getting the error `Syntax error, insert &quot;}&quot; to complete MethodBody.`

Now I have been placing these in trying to get it to work, but so far no luck... Any help would be appreciated.

    public class TheEvoStikLeagueActivity extends Activity {
        private final int SPLASH_DISPLAY_LENGHT = 3000;
         
        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle icicle) {
            super.onCreate(icicle);
            setContentView(R.layout.main);
         
            private boolean checkInternetConnection() {
                ConnectivityManager conMgr = (ConnectivityManager) getSystemService (Context.CONNECTIVITY_SERVICE);
                // ARE WE CONNECTED TO THE NET
                if (conMgr.getActiveNetworkInfo() != null
                        &amp;&amp; conMgr.getActiveNetworkInfo().isAvailable()
                        &amp;&amp; conMgr.getActiveNetworkInfo().isConnected()) {
    
                    return true;
    
                    /* New Handler to start the Menu-Activity
                     * and close this Splash-Screen after some seconds.*/
                    new Handler().postDelayed(new Runnable() {
                        public void run() {
                            /* Create an Intent that will start the Menu-Activity. */
                            Intent mainIntent = new Intent(TheEvoStikLeagueActivity.this, IntroActivity.class);
                            TheEvoStikLeagueActivity.this.startActivity(mainIntent);
                            TheEvoStikLeagueActivity.this.finish();
                        }
                    }, SPLASH_DISPLAY_LENGHT);
                } else {
                    return false;
                       	 
                    Intent connectionIntent = new Intent(TheEvoStikLeagueActivity.this, HomeActivity.class);
                    TheEvoStikLeagueActivity.this.startActivity(connectionIntent);
                    TheEvoStikLeagueActivity.this.finish();
                }
            }
        }
    
                


Android check internet connection

I am running into some issues with the Java socket API. I am trying to display the number of players currently connected to my game.  It is easy to determine when a player has connected.  However, it seems unnecessarily difficult to determine when a player has disconnected using the socket API.

Calling `isConnected()` on a socket that has been disconnected remotely always seems to return `true`.  Similarly, calling `isClosed()` on a socket that has been closed remotely always seems to return `false`.  I have read that to actually determine whether or not a socket has been closed, data must be written to the output stream and an exception must be caught.  This seems like a really unclean way to handle this situation.  We would just constantly have to spam a garbage message over the network to ever know when a socket had closed.

Is there any other solution?

Java socket API: How to tell if a connection has been closed?

I work in a place where each of our internal applications runs on an individual Tomcat instance and uses a specific TCP port. **What would be the best IANA port range to use for these apps in order to avoid port number collisions with any other process on the server?**

Based on http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml, these are the options as I currently see them:

 

 1. System Ports (0-1023): I don&#39;t want to use any of these ports
    because the server may be running services on standard ports in this
    range
 2. User Ports (1024-49151): Given that the applications are internal I don&#39;t intend to request IANA to reserve a number for any of our applications. However, I&#39;d like to reduce the likelihood of the same port being used by another process, e.g., Oracle Net Listener on 1521. 
 3. Dynamic and/or Private Ports (49152-65535): This range is ideal for custom port numbers. My only concern is if this were to happen:
&gt;a. I configure one of my applications to use port X&lt;br /&gt;
&gt;b. The application is down for a few minutes or hours (depending on the nature of the app), leaving the port unused for a little while,&lt;br /&gt;
&gt;c. The operating system allocates port number X to another process, for instance, when that process acts as a client requiring a TCP connection to another server. This succeeds given that it falls within the dynamic range and X is currently unused as far as the operating system is concerned, and&lt;br /&gt;
&gt;d. The app fails to start because port X is already in use

Best TCP port number range for internal applications

    setOnCheckedChangeListener(new OnCheckedChangeListener() {
    			@Override
    			public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
    				// How to check whether the checkbox/switch has been checked
    				// by user or it has been checked programatically ?
    
    				if (isNotSetByUser())
    					return;
    				handleSetbyUser();
    			}
    		});

How to implement method `isNotSetByUser()`?


How can I distinguish whether Switch,Checkbox Value is changed by user or programmatically (including by retention)?

I am using a `HorizontalScrollView` in a layout and I need to identify the user have reached the start and end point of the scroll.

For `ListView` I have tried a the `onScrollListener` and it is possible to find the start and end point of scroll.

I tried to do the same in my `Scrollview` but it seems not possible. Is there any other possible ways to achieve what I need.

Can I have onScrollListener for a ScrollView?

I have a `OnItemSelectedListener` for my `Spinner`, but it is not called when the selected item is the same as the previous one. Apparently the `OnClickListener` is not an option for a `Spinner`.
I need to catch everytime a user click on an item. Any idea?

Maybe the fact that this `Spinner` is inside the `ActionBar` disturbs normal behavior?

    @Override
	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
		inflater.inflate(R.menu.tracklist_menu, menu);
		Spinner spinner = (Spinner) menu.findItem(R.id.option_ordering_spinner)
				.getActionView();
		spinner.setAdapter(mSpinnerAdapter);
		spinner.setSelection(PrefsHelper.getOrderingSpinnerPos(prefs));
		spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

			@Override
			public void onItemSelected(AdapterView&lt;?&gt; parent, View view,
					int position, long id) {
				String str = &quot;selected&quot;;
				System.out.println(str);
				if (optionMenuInitialized) {

					switch (position) {
					case 0:
						// rdm
						getActivity()
								.sendBroadcast(
										new Intent(
												MyIntentAction.DO_RESHUFFLE_PLAYLIST));
						smp.setCurrentTracklistCursorPos(-1);
						trackAdapter.notifyDataSetChanged();
						break;
					case 1:
						// artist
						getActivity()
								.sendBroadcast(
										new Intent(
												MyIntentAction.DO_ORDER_PLAYLIST_BY_ARTIST));
						smp.setCurrentTracklistCursorPos(-1);
						trackAdapter.notifyDataSetChanged();
						break;
					case 2:
						// folder
						getActivity()
								.sendBroadcast(
										new Intent(
												MyIntentAction.DO_ORDER_PLAYLIST_BY_FOLDER));
						smp.setCurrentTracklistCursorPos(-1);
						trackAdapter.notifyDataSetChanged();
						break;
					}
					PrefsHelper.setOrderingSpinnerPos(prefEditor, position);
					prefEditor.commit();
				}
				optionMenuInitialized = true;
			}

			@Override
			public void onNothingSelected(AdapterView&lt;?&gt; parent) {
			}
		});
	}

Spinner : onItemSelected not called when selected item remains the same

I need a solution to properly stop the thread in Java.

I have `IndexProcessor`class which implements the Runnable interface:

    public class IndexProcessor implements Runnable {
    
        private static final Logger LOGGER = LoggerFactory.getLogger(IndexProcessor.class);
    
        @Override
        public void run() {
            boolean run = true;
            while (run) {
                try {
                    LOGGER.debug(&quot;Sleeping...&quot;);
                    Thread.sleep((long) 15000);
    
                    LOGGER.debug(&quot;Processing&quot;);
                } catch (InterruptedException e) {
                    LOGGER.error(&quot;Exception&quot;, e);
                    run = false;
                }
            }
    
        }
    }

And I have `ServletContextListener` class which starts and stops the thread:

    public class SearchEngineContextListener implements ServletContextListener {
    
        private static final Logger LOGGER = LoggerFactory.getLogger(SearchEngineContextListener.class);
    
        private Thread thread = null;
    
        @Override
        public void contextInitialized(ServletContextEvent event) {
            thread = new Thread(new IndexProcessor());
            LOGGER.debug(&quot;Starting thread: &quot; + thread);
            thread.start();
            LOGGER.debug(&quot;Background process successfully started.&quot;);
        }
    
        @Override
        public void contextDestroyed(ServletContextEvent event) {
            LOGGER.debug(&quot;Stopping thread: &quot; + thread);
            if (thread != null) {
                thread.interrupt();
                LOGGER.debug(&quot;Thread successfully stopped.&quot;);
            }
        }
    }

But when I shutdown tomcat, I get the exception in my IndexProcessor class:

    2012-06-09 17:04:50,671 [Thread-3] ERROR  IndexProcessor Exception
    java.lang.InterruptedException: sleep interrupted
    	at java.lang.Thread.sleep(Native Method)
    	at lt.ccl.searchengine.processor.IndexProcessor.run(IndexProcessor.java:22)
    	at java.lang.Thread.run(Unknown Source)

I am using JDK 1.6. So the question is:

How can I stop the thread and not throw any exceptions? 

**P.S.** I do not want to use `.stop();` method because it is deprecated.

How to properly stop the Thread in Java?

In JavaScript, what is the best way to remove a function added as an event listener using bind()?

Example

    (function(){
    
        // constructor
        MyClass = function() {
            this.myButton = document.getElementById(&quot;myButtonID&quot;);
            this.myButton.addEventListener(&quot;click&quot;, this.clickListener.bind(this));
        };
        
        MyClass.prototype.clickListener = function(event) {
            console.log(this); // must be MyClass
        };
        
        // public method
        MyClass.prototype.disableButton = function() {
            this.myButton.removeEventListener(&quot;click&quot;, ___________);
        };
    
    })();

The only way I can think of is to keep track of every listener added with bind.

Above example with this method:

    (function(){
    
        // constructor
        MyClass = function() {
            this.myButton = document.getElementById(&quot;myButtonID&quot;);
            this.clickListenerBind = this.clickListener.bind(this);
            this.myButton.addEventListener(&quot;click&quot;, this.clickListenerBind);
        };
        
        MyClass.prototype.clickListener = function(event) {
            console.log(this); // must be MyClass
        };
        
        // public method
        MyClass.prototype.disableButton = function() {
            this.myButton.removeEventListener(&quot;click&quot;, this.clickListenerBind);
        };
    
    })();

Are there any better ways to do this?

Removing event listener which was added with bind

I am trying to kill a process in the command line for a specific port in ubuntu.

If I run this command I get the port:

    sudo lsof -t -i:9001

so...now I want to run:

    sudo kill &#39;sudo lsof -t -i:9001&#39;

I get this error message:

    ERROR: garbage process ID &quot;lsof -t -i:9001&quot;.
    Usage:
      kill pid ...              Send SIGTERM to every process listed.
      kill signal pid ...       Send a signal to every process listed.
      kill -s signal pid ...    Send a signal to every process listed.
      kill -l                   List all signal names.
      kill -L                   List all signal names in a nice table.
      kill -l signal            Convert between signal numbers and names.

I tried `sudo kill &#39;lsof -t -i:9001&#39;` as well


How to kill a process on a port on ubuntu

From a bash script how can I quickly find out whether a port `445` is open/listening on a server.

I have tried a couple of options, but I want something quick:  
1. `lsof -i :445`  (Takes seconds)  
2. `netstat -an |grep 445 |grep LISTEN` (Takes seconds)  
3. `telnet` (it doesn&#39;t return)  
4. `nmap`, `netcat` are not available on the server  

It will be nice to know of a way that doesn&#39;t enumerate first and greps after that.


Efficiently test if a port is open on Linux?

As the title says, I&#39;m running multiple game servers, and every of them has the same `name` but different `PID` and the `port` number. I would like to match the `PID` of the server which is listening on certain port, and then I would like to kill this process. I need that in order to complete my bash script.

Is that even possible? Because it didn&#39;t find yet any solutions on the web.

Determine the process pid  listening on a certain port

How do you handle multiple client to connect to one server? I have this LogServer.java

    import javax.net.ssl.*;
    import javax.net.*;
    import java.io.*;
    import java.net.*;
    
    public class LogServer {
      private static final int PORT_NUM = 5000;
      public static void main(String args[]) {
        ServerSocketFactory serverSocketFactory =
          ServerSocketFactory.getDefault();
        ServerSocket serverSocket = null;
        try {
          serverSocket =
            serverSocketFactory.createServerSocket(PORT_NUM);
        } catch (IOException ignored) {
          System.err.println(&quot;Unable to create server&quot;);
          System.exit(-1);
        }
        System.out.printf(&quot;LogServer running on port: %s%n&quot;, PORT_NUM);
        while (true) {
          Socket socket = null;
          try {
            socket = serverSocket.accept();
            InputStream is = socket.getInputStream();
            BufferedReader br = new BufferedReader(
              new InputStreamReader(is, &quot;US-ASCII&quot;));
            String line = null;
            while ((line = br.readLine()) != null) {
              System.out.println(line);
            }
          } catch (IOException exception) {
            // Just handle next request.
          } finally {
            if (socket != null) {
              try {
                socket.close();
              } catch (IOException ignored) {
              }
            }
          }
        }
      }
    }

and an embedded applet with part of the code like this e.g

    import java.io.*;
    import java.util.logging.*;
     
    public class LogTest
    {
      private static Logger logger = Logger.getAnonymousLogger();
     
      public static void main(String argv[]) throws IOException
      {
        Handler handler = new SocketHandler(&quot;localhost&quot;, 5000);
        logger.addHandler(handler);
        logger.log(Level.SEVERE, &quot;Hello, World&quot;);
        logger.log(Level.SEVERE, &quot;Welcome Home&quot;);
        logger.log(Level.SEVERE, &quot;Hello, World&quot;);
        logger.log(Level.SEVERE, &quot;Welcome Home&quot;);
      }
    }

now the question is if I run &quot;java LogServer&quot; on the server, it will open the application and waiting for input stream and if I open my site, it will start streaming the log. But if I open one more using other computer/network, the second site does not log the stream. seems like it&#39;s because the first one still bind to port 5000. 

How do I handle this?
How does socket actually work with multiple client / one server?

socket programming multiple client to one server

Update: Already fixed, it seems that one of VirtualHosts configurations files was wrong in sites-enabled.

I have Ubuntu 11.10

When I run the command to start apache2:

    sudo /etc/init.d/apache2 start

I get the following error message:

&gt;  Starting web server apache2                                        
&gt; apache2: Could not reliably determine the server&#39;s fully qualified
&gt; domain name, using 127.0.1.1 for ServerName (98)Address already in
&gt; use: make_sock: could not bind to address 0.0.0.0:80 no listening
&gt; sockets available, shutting down Unable to open logs Action &#39;start&#39;
&gt; failed.

I run this command in order to get the process that is using the port 80:

    sudo netstat -ltnp | grep &#39;:80&#39;

Which returns this output:

    tcp6       0      0 :::80                   :::*                    LISTEN      1176/

To know which process is I run this command:

    ps -wlp1176

That returns: 

    F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
    5 D    33  1176     1  0  80   0 -     0 exit   ?        00:00:00 apache2

But if I try to kill the process: 

    sudo kill -9 1176

It doesn&#39;t kill it, if I run again the netstat command still appears listening and apache start fails.

Any suggestions?

Content Type	Original Author	Original Content on Stackoverflow
Question	Martin Petercak	View Question on Stackoverflow
Solution 1 - Linux	TomT the Weatherman	View Answer on Stackoverflow
Solution 2 - Linux	Mike Mackintosh	View Answer on Stackoverflow
Solution 3 - Linux	Jayan	View Answer on Stackoverflow

Listen on a network port and save data to a text file

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

Solution 3 - Linux

Clone a collection in MongoDB

What's the point of HTML forms `name` attribute?

Attributions