Java Socket OutputStream将一个byte []作为两个单独的消息写入

Question

Trying to send a byte[] through TCP Socket in Java, it sends a specific array as two separate messages, while other arrays are sending as one message. In more details, I convert a hex String to a byte[] using the following function:

public static byte[] hexStringToByteArray(String s) {
        byte[] b = new byte[s.length() / 2];
        for (int i = 0; i < b.length; i++) {
            int index = i * 2;
            int v = Integer.parseInt(s.substring(index, index + 2), 16);
            b[i] = (byte) v;
        }
        return b;
    }

And then I send it through Java TCP Socket:

ServerSocket server = new ServerSocket(3030);
Socket socket = server.accept();
OutputStream out = socket.getOutputStream();
// sample hex string
String msg = "F0700F8000F42400001544952414E00000000000000000000000662000E00060000";
out.write(HexUtiles.hexStringToByteArray(msg));

In debugging the code I found out it separate the array in byte number 1024. Also, increasing and decreasing the socket buffer size made no differences.

In addition, there is no 0A (Hex String of \\n ) in the message! I guess there is some strange behavior in the write method that sends a byte[] array as two messages! How can I send the byte[] as only one message?

Answer 1

There are no "messages" in TCP. Everything is sent as a stream and it's undefined how it will be chunked on the other end. Chunks might be split or joined together.

Send the byte size before each array using DataOutputStream . Read the size on the other end using DataInputStream and then that many bytes. This way you will be able to recreate your arrays at the other end.

Another option is to use ObjectOutputStream and ObjectInputStream and send the arrays as objects.