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Eclipse - Functions issue [duplicate]

This question already has answers here:
How do I compare strings in Java?
(23 answers)
Closed 8 years ago.
I'm trying to get text from server and then check it a to know what actions to take with the text adopted. The problem is that when I try to check if the received text for example is "Exited" the query always return the value "false" when the received text is really "Exited".
Here is the code :
class Get_Message_From_Server implements Runnable
{
public void run()
{
InputStream iStream = null;
try
{
iStream = Duplex_Socket_Acceptor.getInputStream();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
//Create byte array of size image
byte[] Reading_Buffer = null;
try
{
Reading_Buffer = new byte [Duplex_Socket_Acceptor.getReceiveBufferSize()];
//New_Buffer = new byte [100];
}
catch (IOException e1)
{
// TODO Auto-generated catch block
e1.printStackTrace();
}
byte[] Byte_Char_1 = new byte[1];
int Byte_String_Lenght = 0;
//read size
try
{
iStream.read(Reading_Buffer);
String Reading_Buffer_Stream_Lenghtor = new String(Reading_Buffer);
//System.out.println("full : " + Reading_Buffer_Stream_Lenghtor);
Byte_String_Lenght = Reading_Buffer_Stream_Lenghtor.indexOf(new String(Byte_Char_1));
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
//Convert to String
Meassage = new String(Reading_Buffer);
Meassage = Meassage.substring(0, Byte_String_Lenght);//The text that received
Message_Getted = 1;
}
}
The query :
if(Message_1 != "Exited")//the message query
{
System.out.println("Continued 253");
continue;
}
Its always return the value - false
its important to know that the message is in Utf - 8 encoding
so how i can to fix the issue ?

If you compare strings by using oparators, Java will not look at the contents of the string but at the reference in memory. To compare String content in Java, you should use the following:
String Message_1; // Hopefully has a value sent by the server
if(Message_1.equals("Exited")) {
// Do stuff when exited
} else {
// Do stuff when not exited
}

String is a variable - and variables should start with lower Case letter - Please read Java Code conventions. Also to check if your message contains string you thing it should just do System.out.println(Message_1); and if the message contains what you expect you compare string doing
if(Message_1.equals("Exited")) {
System.out.println("Yes they are equal");
} else {
System.out.println("No they are not");
}
If this will print "No they are not" that simply means that your variable Message_1 is not what you think it is.. As simple as that. There is no such a thing as .equals method does not work. Its your variable that doesn't ;)

Method "lock" the entire screen when a socket server is started

Below is the receive method that implements a socket server and works perfectly.
private void Receive(){
log.info("Server started - waiting for the clients.");
try {
Boolean end = false;
ServerSocket ss = new ServerSocket(12345);
while(!end){
//Server is waiting for client here, if needed
Socket s = ss.accept();
BufferedReader input = new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter output = new PrintWriter(s.getOutputStream(),true); //Autoflush
String st = input.readLine();
JSONObject jsonObj;
try {
jsonObj = new JSONObject(st);
long id = jsonObj.optLong("DeviceID", count.addAndGet(1) );
String name = jsonObj.toString();
table.put(id, name);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
etResult.setText(st);
Log.d("Tcp Example", "From client: "+st);
output.println("Response from Sever: Connectivity ok");
s.close();
if (st != null ){ end = true; }
}
ss.close();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
The only problem is, when I hit the button to call that method, the socket starts listening and waits for a client messages. While it does not happen, the app remains freezes and I try to hit any other button, the app may crashes.
Does anyone have a hint about how could handle it and leave the socket listening in "background" withou locking the entire screen?
thank you

Make a thread or AsyncTask and do all the socket functions on that. IF it's something you're going to rarely do and want to fire it off and process the results, use an AsyncTask. If it's something you're going to want to do constantly and don't want to run multiple workers at the same time or have multiple workers queued up, use a Thread.

Android TCP app hanging on inStream.readline()

This is a continuation of this question because it my orginal question was answered, but it did not solve the bug.
Question:
How do I fix the code hanging on this line inStream.readline()
My Intent:
This is in a thread that will loop through checking if there is an outMessage, if there is, it will send the message.
Next it will check it if there is anything in the in-stream, if there is, it will send it to the handler in my main activity.
Lastly, it will sleep for 1 second, then check again.
This should allow me to read/write multiple times without needing to close and open the socket.
Problem:
It is reading and writing better, but still not working properly
What is happening now:
If outMessage is initialized with a value, upon connection with the server, the socket:
writes and flushes the value (server receives & responds)
updates value of outMessage (to null or to "x" depending on how i have it hard-coded)
reads and shows the response message from the server
re-enters for the next loop
IF i set outMessage to null, it skips over that if statements correctly then hangs; otherwise, if i set outMessage to a string (lets say "x"), it goes through the whole if statement, then hangs.
The code it hangs on is either of the inStream.readline() calls (I currently have one commented out).
Additional info:
- once connected, I can type in the "send" box, submit (updates the outMessage value), then disconnect. Upon re-connecting, it will read the value and do the sequence again until it get stuck on that same line.
Changes since the referenced question:
- Made outMessage and connectionStatus both 'volatile'
- added end-of-line delimiters in neccesary places.
Code:
public void run() {
while (connectionStatus != TCP_SOCKET_STATUS_CONNECTED) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
while (connectionStatus == TCP_SOCKET_STATUS_CONNECTED) {
try {
if (outMessage != null){
OutStream.writeBytes(outMessage + "\n");
OutStream.flush();
sendMessageToAllUI(0, MAINACTIVITY_SET_TEXT_STATE, "appendText" , "OUT TO SERVER: " + outMessage);
outMessage = "x";
}
Thread.sleep(100);
// if (InStream.readLine().length() > 0) {
String modifiedSentence = InStream.readLine();
sendMessageToAllUI(0, MAINACTIVITY_SET_TEXT_STATE, "appendText" , "IN FROM SERVER: " + modifiedSentence);
// }
Thread.sleep(1000);
} catch (IOException e) {
connectionLost();
break;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
The thread that makes the socket:
public void run() {
setName("AttemptConnectionThread");
connectionStatus = TCP_SOCKET_STATUS_CONNECTING;
try {
SocketAddress sockaddr = new InetSocketAddress(serverIP, port);
tempSocketClient = new Socket(); // Create an unbound socket
// This method will block no more than timeoutMs. If the timeout occurs, SocketTimeoutException is thrown.
tempSocketClient.connect(sockaddr, timeoutMs);
OutStream = new DataOutputStream(tempSocketClient.getOutputStream());
InStream = new BufferedReader(new InputStreamReader(tempSocketClient.getInputStream()));
socketClient = tempSocketClient;
socketClient.setTcpNoDelay(true);
connected();
} catch (UnknownHostException e) {
connectionFailed();
} catch (SocketTimeoutException e) {
connectionFailed();
} catch (IOException e) {
// Close the socket
try {
tempSocketClient.close();
} catch (IOException e2) {
}
connectionFailed();
return;
}
}
Server:
public static void main(String[] args) throws IOException {
String clientSentence;
String capitalizedSentence;
try {
ServerSocket welcomeSocket = new ServerSocket(8888);
SERVERIP = getLocalIpAddress();
System.out.println("Connected and waiting for client input!\n Listening on IP: " + SERVERIP +"\n\n");
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
while(true)
{
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
clientSentence = inFromClient.readLine();
System.out.println("clientSentance == " + clientSentence);
String ip = connectionSocket.getInetAddress().toString().substring(1);
if(clientSentence != null)
{
System.out.println("In from client ("+ip+")("+ System.currentTimeMillis() +"): "+clientSentence);
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeBytes(capitalizedSentence + '\n');
System.out.println("Out to client ("+ip+"): "+capitalizedSentence);
}
}
} catch (IOException e) {
//if server is already running, it will not open new port but instead re-print the open ports information
SERVERIP = getLocalIpAddress();
System.out.println("Connected and waiting for client input!\n");
System.out.println("Listening on IP: " + SERVERIP +"\n\n");
}
}
Thanks in advance!
Edits:
added the server code after updating
I tried messing around with setting the SoTimout for the socket but took that back out

Your server is specifically designed to receive exactly one line from a client and send exactly one line back. Look at the code:
while (true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(
new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(
connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
String ip = connectionSocket.getInetAddress().toString()
.substring(1);
System.out.println("In from client (" + ip + "): "
+ clientSentence);
if (clientSentence != null) {
capitalizedSentence = clientSentence.toUpperCase() + '\n';
System.out.println("Out to client (" + ip + "): "
+ capitalizedSentence);
outToClient.writeBytes(capitalizedSentence + "\n");
}
Notice that inside the loop it accepts a new connection, reads exactly one line, and then writes exactly one line. It doesn't close the connection. It doesn't sanely end the conversation. It just stops reading.
A client that worked with this server would have to connect, send exactly one line, read exactly one line back, and then the client would have to close the connection. Your client doesn't do that. Why? Because you had no idea that's what you had to do. Why? Because you had no design ... no plan.
So that's your specific issue. But please, let me urge you to take a huge step back and totally change your approach. Before you write a single line of code, please actually design and specify a protocol at the byte level. The protocol should say what data is sent, how messages are delimited, who sends when, who closes the connection, and so on.
Otherwise, it's impossible to debug your code. Looking at the server code above, is it correct? Well, who knows. Because it's unclear what it's supposed to do. When you wrote the client, you assumed the server behaved one way. Was that assumption valid? Is the server broken? Who knows, because there's no specification of what the server is supposed to do.

You need to check if there is data available:
if (InStream.available > 0) {
String modifiedSentence = InStream.readLine();
sendMessageToAllUI(0, MAINACTIVITY_SET_TEXT_STATE, "appendText" , "IN FROM SERVER: " + modifiedSentence);
}
But to be honest, even that is not ideal because you have no gurantee that the eond-of-line will have been received. If the server sends a few bytes but never sends the end-of-line then you will still be blocking forever. Production socket code should never rely on readLine but instead read into a buffer and check that buffer for end-of-line (or whatever criteria your protocol needs).
Didn't read closely enough, I thought InStream was an InputStream instance. InputStream has available. InputStreamReader has ready (which in turn calls InputStream.available. As long as you keep a refernce to either of these then you can see if data is available to be read.

Can't receive mails with Pop in Android

I can receive my mails with Imap with this code sample :
URLName server = new URLName("imaps://" + username + ":"+ password + "#imap.gmail.com/INBOX");
Session session = Session.getDefaultInstance(new Properties(), null);
Folder folder = session.getFolder(server);
if (folder == null)
{
System.exit(0);
}
folder.open(Folder.READ_ONLY);
Message[] messages = folder.getMessages();
But sometimes Imap doesn't give any service and at those times I want to use Pop but I couldn't use it with my code. It is different the other codes for using receive mail. But in Android only this code is working.
What should I change in this code to work with Pop?

First, there's a nice URLName constructor that takes all the component pieces as separate parameters, so you don't have to do string concatenation.
Switch from IMAP to POP3 requires changing the protocol name as well as the host name. See the JavaMail FAQ for examples. The protocol name is "pop3s" and the host name is "pop.gmail.com".
Finally, you should use Session.getInstance instead of Session.getDefaultInstance. Compare the javadocs for the two methods to understand why.

How about this one.Really worked for me!!(Source:here)
String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";
Properties pop3Props = new Properties();
pop3Props.setProperty("mail.pop3.socketFactory.class", SSL_FACTORY);
pop3Props.setProperty("mail.pop3.socketFactory.fallback", "false");
pop3Props.setProperty("mail.pop3.port", "995");
pop3Props.setProperty("mail.pop3.socketFactory.port", "995");
URLName url = new URLName("pop3", "pop.gmail.com", 995, "","youremailid#gmail.com",yourpassword);
Session session = Session.getInstance(pop3Props, null);
Store store = new POP3SSLStore(session, url);
try {
store.connect();
} catch (MessagingException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
Folder folder = null;
try {
folder = store.getDefaultFolder();
folder = folder.getFolder("INBOX");
} catch (MessagingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (folder == null) {
System.exit(0);
}
try {
folder.open(Folder.READ_ONLY);
} catch (MessagingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Try retreiving folder via store object.And also mention that the folder you wish to retreive is INBOX!Also note that in settings,port number is 995 form pop.(You may leave the first six lines as they are.)

getSocketAddress() method causes delay which leads to communication lag in Android

I'm developing a UDP responder to handle basic SSDP commands. The purpose of this piece of code is to do auto discovery, so when the server sends a multicast to a specific group all other subscribed devices should send back a UDP packet announcing its presence to the host and port of who sent the multicast. My android device receives and sends the packet just fine but because it takes too long to get back the SocketAddress object from getSocketAddress() method the server times out, closes the listening port and never gets a packet back from the android device.
Here's my code:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
MulticastSocket ms = null;
byte[] packBuf = new byte[128];
try {
ms = new MulticastSocket(32410);
ms.joinGroup(InetAddress.getByName("239.255.255.250"));
} catch (IOException e3) {
// TODO Auto-generated catch block
e3.printStackTrace();
}
while (true)
{
DatagramPacket receivedPack = new DatagramPacket(packBuf, packBuf.length);
try {
ms.receive(receivedPack);
Log.d(TAG, "Received data");
} catch (IOException e3) {
// TODO Auto-generated catch block
e3.printStackTrace();
}
String responseStr = "HTTP/1.0 200 OK\n" +
"Content-Type: app\n" +
"Resource-Identifier: 945e7dd5913ab45f1db4f271a1620b9471fb7d4d\n" +
"Name: Test App\n" +
"Port: 8888\n" +
"Updated-At: 1319511680\n" +
"Version: 0.9.3.4-29679ad\n" +
"Content-Length: 23\n\n" +
"<message>test</message>";
byte[] response = responseStr.getBytes();
DatagramSocket sendSocket = null;
try {
sendSocket = new DatagramSocket();
} catch (IOException e2) {
// TODO Auto-generated catch block
Log.e(TAG,"Erro",e2);
}
DatagramPacket outPack;
try {
outPack = new DatagramPacket(response, responseStr.length(), receivedPack.getSocketAddress());
sendSocket.send(outPack);
} catch (UnknownHostException e1) {
Log.e(TAG,"Erro",e1);
}
catch (IOException e) {
Log.e(TAG,"Erro",e);
}
catch (Exception e)
{
Log.e(TAG,"Erro",e);
}
}
}
Any ideas?
thanks in advance,
fbr

The most likely problem is that getSocketAddress() is trying to resolve the DNS name of the IP address, which is timing out either due to it being a multicast address or just general DNS lag.
The InetSocketAddress class has a constructor option needResolved which can control this behavior. Unfortunately, it does not appear that DatagramPacket.getSocketAddress() allows you to specify that you want that set to false.
This is apparently a known issue, with some recent discussion of it here:
Issue 12328: DatagramChannel - cannot receive without a hostname lookup
The thread suggests that this has been fixed in Android 3.0, and offers a couple of workarounds for Android 2.0 which may or may not work.
In your case, you could try creating an InetSocketAddress set to INADDR_ANY and port 0 with needsResolved set to 0, and then pass that in when you create receivedPack. Hopefully receive() will reuse that and remember the setting.

2 things come to mind...
1) What happens when you change:
outPack = new DatagramPacket(response, responseStr.length(), receivedPack.getSocketAddress());
to
outPack = new DatagramPacket(response, responseStr.length(), receivedPack.getAddress(), receivedPack.getPort());
2) I remember having this sort of problem with an embedded Java on a Home Automation system. Our short term solution was to put most of the machine and multicast addresses in the hosts file. Long term we ended up with a local DNS server.
There is a parameter somewhere in the Java Network stack that tells it how long to cache DNS failures in memory. We cranked that number up to, I think, 5 minutes instead of 10 seconds.