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Pass Uint8List from dart to java over a TCPSocket

I need to pass an Uint8List to a byte[] array in java over a TCPSocket. There is size mismatch at both ends. PS: I am a beginner in dart.
I have tried socket.add(buf), socket.write(buf), socket.writeAll(buf) but none of them worked
Code in Flutter side (TCP client)
void readVoiceData(Uint8List buf) {
print("Send data size:"+buf.lengthInBytes.toString());
socket.add(buf);
}
OUTPUT: Send data size: 1280
Code Snippet on java side (TCP server)
in = new DataInputStream(clientSocket.getInputStream());
Log.d(TAG, "****Opened InputStream*******");
while (!isInterrupted()) {
if (mTrack != null) {
try {
in.read(bytes);
Log.d(TAG, "Received data size"+bytes.length);
}
}
OUTPUT: Received data size: 1
I am sure the socket connection has been established correctly as I am able to send Strings and Integers flawlessly over them.

This happens because the read() method of the FilterInputStream (DataInput is his son) reads just the next avaliable byte.
Thou, if you want to get the total size of the InputStream, do something like:
size = in.available(); //returns an estimate of number of bytes avaliable on the stream
buf = new byte[size];
realLength= in.read(buf, 0, size);
This code snippet is taken from here.

Java Socket handling in Android different than on other platforms?

I have a very strange situation. I connect my Java software with a device, let´s call it "Black Box" (because I cannot look into it or make traces within it). I am adressing a specific port (5550) and send commands as byte sequences on a socket. As a result, I get an answer from the Black Box on the same socket.
Both my commands and the replies are prefixed in a pre-defined way (according to the API) and have an XOR checksum.
When I run the code from Windows, all is fine: Command 1 gets its Reply 1 and Command 2 gets its Reply 2.
When I run the code from Android (which is actually my target - Windows came into play to track down the error) it gets STRANGE: Command 1 gets its Reply 1 but Command 2 does not. When I play with Command 2 (change the prefix illegally, violate the checksum) the Black Box reacts as expected (with an error reply). But with the correct Command 2 being issued from Android, the Reply is totally mis-formed: Wrong prefix and missing checksum.
In the try to analyse the error I tried WireShark and this shows that on the network interface, the Black Box is sending the RIGHT Reply 2, but evaluating this reply in Java from the socket, it is wrong. How can this be when all is fine for Command/Reply 1???
Strange is, that parts of the expected data are present:
Expected: ff fe e4 04 00 11 00 f1
Received: fd fd fd 04 00 11 00 // byte 8 missing
I am attaching the minimalistic code to force the problem. What could falsify the bytes which I receive? Is there a "raw" access in Java to the socket which could reveal the problem?
I am totally confused so any help would be appreciated:
String address = "192.168.1.10";
int port = 5550;
Socket socket;
OutputStream out;
BufferedReader in;
try {
socket = new Socket(address, port);
out = socket.getOutputStream();
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// This is "Command 1" which is receiving the right reply
// byte[] allesAn = new byte[] {(byte)0xff, (byte)0xfe, (byte)0x21, (byte)0x81, (byte)0xa0};
// out.write(allesAn);
// This is "Command 2" which will not receive a right reply
byte[] getLokInfo3 = new byte[] {(byte)0xff, (byte)0xfe, (byte)0xe3, (byte)0, (byte)0, (byte)3, (byte)0xe0};
out.write(getLokInfo3);
out.flush();
while (true) {
String received = "";
final int BufSize = 1000;
char[] buffer = new char[BufSize];
int charsRead = 0;
charsRead = in.read(buffer, 0, BufSize);
// Convert to hex presentation
for (int i=0; i < charsRead; i++) {
byte b = (byte)buffer[i];
received += hexByte((b + 256) % 256) + " ";
}
String result = charsRead + ">" + received + "<";
Log.e("X", "Read: " + result);
}
} catch (Exception e) {
Log.e("X", e.getMessage() + "");
}
with
private static String hexByte(int value) {
String s = Integer.toHexString(value);
return s.length() % 2 == 0 ? s : "0" + s;
}
Here is what wireshark says, showing the expected 8 bytes:

How to read (all available) data from serial connection when using JSSC?

I'm trying to work with JSSC.
I built my app according to this link:
https://code.google.com/p/java-simple-serial-connector/wiki/jSSC_examples
My event handler looks like:
static class SerialPortReader implements SerialPortEventListener {
public void serialEvent(SerialPortEvent event) {
if(event.isRXCHAR()){//If data is available
try {
byte buffer[] = serialPort.readBytes();
}
catch (SerialPortException ex) {
System.out.println(ex);
}
}
}
}
}
The problem is that I'm always not getting the incoming data in one piece. (I the message has a length of 100 bytes, Im getting 48 and 52 bytes in 2 separates calls)
- The other side send me messages in different lengths.
- In the ICD Im working with, there is a field which tell us the length of the message. (from byte #10 to byte #13)
- I cant read 14 bytes:
(serialPort.readBytes(14);,
parse the message length and read the rest of the message:
(serialPort.readBytes(messageLength-14);
But if I will do it, I will not have the message in once piece (I will have 2 separates byte[] and I need it in one piece (byte[]) without the work of copy function.
Is it possible ?
When working with Ethernet (SocketChannel) we can read data using ByteBuffer. But with JSSC we cant.
Is there a good alternative to JSSC ?
Thanks

You can't rely on any library to give you all the content you need at once because :
the library dont know how many data you need
the library will give you data as it comes and also depending on buffers, hardware, etc
You must develop your own business logic to handle your packets reception. It will of course depend on how your packets are defined : are they always the same length, are they separated with same ending character, etc.
Here is an example that should work with your system (note you should take this as a start, not a full solution, it doesn't include timeout for example) :
static class SerialPortReader implements SerialPortEventListener
{
private int m_nReceptionPosition = 0;
private boolean m_bReceptionActive = false;
private byte[] m_aReceptionBuffer = new byte[2048];
#Override
public void serialEvent(SerialPortEvent p_oEvent)
{
byte[] aReceiveBuffer = new byte[2048];
int nLength = 0;
int nByte = 0;
switch(p_oEvent.getEventType())
{
case SerialPortEvent.RXCHAR:
try
{
aReceiveBuffer = serialPort.readBytes();
for(nByte = 0;nByte < aReceiveBuffer.length;nByte++)
{
//System.out.print(String.format("%02X ",aReceiveBuffer[nByte]));
m_aReceptionBuffer[m_nReceptionPosition] = aReceiveBuffer[nByte];
// Buffer overflow protection
if(m_nReceptionPosition >= 2047)
{
// Reset for next packet
m_bReceptionActive = false;
m_nReceptionPosition = 0;
}
else if(m_bReceptionActive)
{
m_nReceptionPosition++;
// Receive at least the start of the packet including the length
if(m_nReceptionPosition >= 14)
{
nLength = (short)((short)m_aReceptionBuffer[10] & 0x000000FF);
nLength |= ((short)m_aReceptionBuffer[11] << 8) & 0x0000FF00;
nLength |= ((short)m_aReceptionBuffer[12] << 16) & 0x00FF0000;
nLength |= ((short)m_aReceptionBuffer[13] << 24) & 0xFF000000;
//nLength += ..; // Depending if the length in the packet include ALL bytes from the packet or only the content part
if(m_nReceptionPosition >= nLength)
{
// You received at least all the content
// Reset for next packet
m_bReceptionActive = false;
m_nReceptionPosition = 0;
}
}
}
// Start receiving only if this is a Start Of Header
else if(m_aReceptionBuffer[0] == '\0')
{
m_bReceptionActive = true;
m_nReceptionPosition = 1;
}
}
}
catch(Exception e)
{
e.printStackTrace();
}
break;
default:
break;
}
}
}

After writing data to serial port it need to be flushed. Check the timing and pay attention to the fact that read should occur only after other end has written. read size is just an indication to read system call and is not guaranteed. The data may have arrived and is buffered in serial port hardware buffer but may not have been transferred to operating system buffer hence not to application. Consider using scm library, it flushes data after each write http://www.embeddedunveiled.com/

Try this:
Write your data to the serial port (using serialPort.writeBytes()) and if you are expecting a response, use this:
byte[] getData() throws SerialPortException, IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] b;
try {
while ((b = serialPort.readBytes(1, 100)) != null) {
baos.write(b);
// System.out.println ("Wrote: " + b.length + " bytes");
}
// System.out.println("Returning: " + Arrays.toString(baos.toByteArray()));
} catch (SerialPortTimeoutException ex) {
; //don't want to catch it, it just means there is no more data to read
}
return baos.toByteArray();
}
Do what you want with the returned byte array; in my case I just display it for testing.
I found it works just fine if you read one byte at a time, using a 100ms timeout, and when it does time out, you've read all data in the buffer.
Source: trying to talk to an Epson serial printer using jssc and ESC/POS.

Sending ints, receives wrong data

I'm trying to send the player's position (x, y) to the client from the Server. Everything else seems to work, but not these 2 ints. I can send other integers, for example 3456, and it will receive 3456. But these wont work.
Server Java code:
public void sendAccountInformation() throws IOException {
dos.write(player.id);
main.log(player.id);
dos.println(player.username);
main.log(player.username);
dos.write(player.x);
main.log(player.x);
dos.write(player.y);
main.log(player.y);
dos.write(player.mapid);
main.log(player.mapid);
dos.flush();
}
Server output:
0
sdfsdffsd
544
384
0
The above is the correct information that should be sent.
Client Java code:
public void loadAccount() throws IOException {
int id = dis.read();
main.player = new Player(id, main);
main.log(id);
main.player.username = dis.readLine();
main.log(main.player.username);
main.player.x = dis.read();
main.log(main.player.x);
main.player.y = dis.read();
main.log(main.player.y);
main.player.mapid = dis.read();
main.log(main.player.mapid);
}
Client output:
0
sdfsdffsd
63
63
0
As you can see, the two integers (544 and 384) was changed into (63 and 63). But EVERYTHING else sends and is received correctly?

I believe you should try using writeInt() and readInt() to write and read int.

How to separate data being received over bluetooth in android

I have modified the BluetoothChat example code to connect to a generic bluetooth transceiver which I have connected to the UART on a TI MSP430 development board. I have established communication and can send and receive a single string and display the value in a TextView. Below is the C code that I'm using to send the 1-3 digit value for pressure, temp1 and temp 2. It is fairly straightforward, and I is working as designed.
for(int i = 0; i <= 2; i++) // send pressure value
{
UCA0TXBUF = pressureString[i];
while(!(IFG2 & UCA0TXIFG));
}
for(int i = 0; i <= 2; i++) // send temp1 value
{
UCA0TXBUF = tempOneString[i];
while(!(IFG2 & UCA0TXIFG));
}
for(int i = 0; i <= 2; i++) // send temp2 value
{
UCA0TXBUF = tempTwoString[i];
while(!(IFG2 & UCA0TXIFG));
}
Now I want to send multiple pieces of data to the android device and have them displayed according to their data type in a separate TextView for each value. For right now I am measuring two temperature sensors and a pressure sensor. I have sent all of the data to the android device with no problems, but all the values just overwrite each other in the TextView so that only the last string sent is displayed.
This is the portion of code that runs while connected to a remote device:
/**
* This thread runs during a connection with a remote device.
* It handles all incoming and outgoing transmissions.
*/
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
Log.d(TAG, "create ConnectedThread");
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the BluetoothSocket input and output streams
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
Log.e(TAG, "temp sockets not created", e);
}
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
public void run() {
Log.i(TAG, "BEGIN mConnectedThread");
byte[] buffer = new byte[1024];
int bytes;
// Keep listening to the InputStream while connected
while (true) {
try {
// Read from the InputStream
bytes = mmInStream.read(buffer);
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
connectionLost();
break;
}
}
}
This is the code that reads the message and displays it in the TextView:
case MESSAGE_READ:
byte[] readBuf = (byte[]) msg.obj;
// construct a string from the valid bytes in the buffer
String readMessage = new String(readBuf, 0, msg.arg1);
mTextView.setText(readMessage); //added by AMJ in attempt to display variable in textview
break;
I can't seem to figure out how to program the android application to be able to tell the difference between strings, so that when I receive the Temp1 string it goes to the Temp1TextView, and Temp2 string goes to Temp2TextView, etc. Should I add a special character as the first bit sent from the MSP430, and reference that bit in Android to identify where it should go? Just a thought.
Any help is much appreciated.
EDIT: I figured I could try and convert the int to a string, then use the tokenizer to separate it, and then convert it back to an int. However, the application is now crashing when it receives data over bluetooth. Here is the code that I'm using to convert it. Any idea why it may be crashing?
bytes = mmInStream.read(buffer);
byteString = String.valueOf(bytes);
StringTokenizer tokens = new StringTokenizer(byteString, ":");
String first = tokens.nextToken(); // this will contain exhaust temp
String second = tokens.nextToken(); // this will contain damper position
separatebytes1 = Integer.valueOf(first);
separatebytes2 = Integer.valueOf(second);
// Read from the InputStream
// bytes = mmInStream.read(buffer);
// Send the obtained bytes to the UI Activity
// mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer)
// .sendToTarget();
mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, separatebytes1, -1, buffer)
.sendToTarget();
This is the logcat from the crash:
W/dalvikvm(24850): threadid=11: thread exiting with uncaught exception (group=0x
411ae300)
E/AndroidRuntime(24850): FATAL EXCEPTION: Thread-1286
E/AndroidRuntime(24850): java.util.NoSuchElementException
E/AndroidRuntime(24850): at java.util.StringTokenizer.nextToken(StringTok
enizer.java:208)
E/AndroidRuntime(24850): at com.example.android.BluetoothChat.BluetoothCh
atService$ConnectedThread.run(BluetoothChatService.java:411)
W/ActivityManager( 270): Force finishing activity com.example.android.Bluetoo
thChat/.BluetoothChat

You either have a single message with several values in pre-defined order, or you'll have to tell the receiver (app) which value is being sent next, more or less as you suggested.

The crash (regarding your edited question) occurs likely because byteString does not contain a ":". If this is the case, your
String second = tokens.nextToken()
will throw exactly the Fatal Exception you posted.
So, before you separate the string with tokens.nextToken(), check how many Tokens are in the bytestring with:
tokens.countTokens