Issue sending an array of bytes representing an integer from c# to java client

Question

I am trying to send an array of byte representing an integer from a c# ASP.Net page to a java client as follows

public void WriteToStream(int i)
{
    byte[] buffer = BitConverter.GetBytes(i);
    var writer = new MemoryStream();
    // Little - Endians to Big - Endians;
    Array.Reverse(buffer);
    // Unsigned Char to Signed Char
    sbyte[] suffer = (sbyte[])(Array)buffer;
    BinaryWriter binaryWriter = new BinaryWriter(writer);
    foreach (var sb in suffer)
    {
        binaryWriter.Write(sb);
    }
    binaryWriter.Close();
    buffer = writer.ToArray();
    writer.Close();
    // Writing to an Aspx Page Response Output Stream
    Response.OutputStream.Write(buffer, 0, buffer.Length);
}

and on java side

public int getInt(byte[] data)
{
    byte[] buffer;
    ByteArrayInputStream reader = new ByteArrayInputStream(data);
    buffer = new byte[4];
    reader.read(buffer, 0, 4);
    int i = ByteBuffer.wrap(buffer).getInt();
    return i;
}

These procedures work correctly for integers less than 128 but for 128 the java side returns 239. I know that the issue is related to the fact that java memory storage is Big – Endians Signed Bytes while .Net C# is Little – Endians Unsigned Bytes. I’m also aware of the following posts

Get int from bytes in Java, encoded first in C#

different results when converting int to byte array - .NET vs Java

Java and C# - byte array to long conversion difference

however I cannot change the java side as the above posts suggest. I have to modify C# side to suit other end.

How may I do that?

[UPDATED]

I changed the C# side based on MiscUtil as follows

public void WriteToStream(int i)
{
    var stream = new MemoryStream();
    var writer = new EndianBinaryWriter(EndianBitConverter.Big, stream);
    writer.Write(i);
    byte[] buffer = stream.ToArray();
    // Writing to an Aspx Page Response Output Stream
    Response.OutputStream.Write(buffer, 0, buffer.Length);
}

however the result has not changed. Java still returns 239 (while expecting 128)

Why? and how may I correct it?

128 going to 239 suggest something other than endianess is causing a problem. I suggest you output the byte stream in hex formatted bytes and make sure that the data going into the connection is correct and matches the data coming out of the connection before converting the bytes into ints. — BevynQ, Sep 08 '13 at 22:33

score 0 · Answer 1 · answered Sep 08 '13 at 22:30

0

Easy. Use Jon Skeet's EndianBinaryWriter, available as part of MiscUtil.

answered Sep 08 '13 at 22:30

spender

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Thanks for your answer. I've updated the question to reflect your suggestion however the problem is still there. Would you please have look at that to see where I may make mistake? Thanks again. – anonim Sep 08 '13 at 23:34

score 0 · Answer 2 · edited May 23 '17 at 12:20

If you see that the number between -128 and 127 work fine but anything higher that 128 does not work is because one of the sides is handling the bytes as signed.

For this I suggest that on your C# side you use the getbuffer method that returns unsigned bytes

http://msdn.microsoft.com/en-us/library/system.io.memorystream.getbuffer.aspx

And also for the JAVA side you can take a look at the USIGNED LINK that is mentioned on this answer

Converting raw-byte values into Java types

Issue sending an array of bytes representing an integer from c# to java client

2 Answers2