CODEWITHSUNDEEP
javac#byteunsignedsigned
Richard Whitehouse
Richard Whitehouse

Reputation: 691

C# to Java Byte Conversion

I'm attempting to build a TCP Client in C# that passes over files (mainly MP3) over to an Android application, but I'm having great difficulty converting between unsigned and signed bytes.

What am I doing wrong to get the mismatch in values retrieved by the app?

The below is the data C# is sending across via TCP. 

new byte[] { 9, 1, 251, 252, 253, 254, 255, 254, 253, 252, 251, }

Java

while ((charsRead = in.read(buffer)) != -1)
{
    serverMessage = new String(buffer).substring(0, charsRead);
    serverByteMessage = serverMessage.getBytes();
    for(int i = 0; i < serverByteMessage.length; i++) {
        int bi = serverByteMessage[i] & 0xFF;
        Log.e("TCP Client", "Item: " + serverByteMessage[i]);
        Log.e("TCP Client", "Value of my test unsigned byte: " + bi);
    }
}

Java Output

Item: 9
Value of my test unsigned byte: 9
Item: 1
Value of my test unsigned byte: 1
Item: -17
Value of my test unsigned byte: 239
Item: -65
Value of my test unsigned byte: 191
Item: -67
Value of my test unsigned byte: 189
Item: -17
Value of my test unsigned byte: 239
Item: -65
Value of my test unsigned byte: 191
Item: -67
Value of my test unsigned byte: 189
Item: -17
Value of my test unsigned byte: 239
Item: -65
Value of my test unsigned byte: 191
Item: -67
Value of my test unsigned byte: 189
Item: -17
Value of my test unsigned byte: 239
Item: -65
Value of my test unsigned byte: 191
Item: -67
Value of my test unsigned byte: 189
Item: -17
Value of my test unsigned byte: 239

Upvotes: 1

Views: 887

Answers (1)

Peter Lawrey
Peter Lawrey

Reputation: 533720

When you convert binary to text, you can only convert valid byte encodings to text. If you convert random data to text, any invalid code are typically replaced with a ?

The simple solution is to avoid mixing text and binary unless you really know what you are doing.

InputStream in = socket.getInputStream();
int bytesRead;
byte[] bytes = new bytes[512];
while((bytesRead = in.read(bytes)) > 0) {
   for (int i =0; i < bytesread; i++) {
       int bi = bytesRead[i] & 0xFF;
       System.out.println(bi);
   }
}

Note: You cannot assume that TCP supports messages. It only supports a stream of bytes. Your have to have a protocol which allows you to work out when a message starts/finishes. e.g. you should send the length of the message before the actual message.

Upvotes: 1

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