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javanio

Why I get a lot of unwanted output when I convert ByteBuffer to String?

I write a UDP server to receive messages from clients using NIO:

DatagramChannel channel = DatagramChannel.open();
channel.socket().bind(new InetSocketAddress(9999));
ByteBuffer buf = ByteBuffer.allocate(1024);
buf.clear();
while (channel.receive(buf) != null) {
      System.out.println("---has received data:" + new String(buf.array(), ASCII));
      buf.clear();
}

then I use nc command to send some data to the UDP server

nc -u 127.0.0.1 9999 < ./test.txt

there is only one line in test.txt

#cat ./test.txt
12345678

and the output of the server is like this enter image description here

so how could I get the 12345678 string and remove the following '口' things?

Solution 
  • DatagramChannel channel = DatagramChannel.open();
channel.socket().bind(new InetSocketAddress(9999));

ByteBuffer chunkData = ByteBuffer.allocate(1024);
chunkData.clear();

channel.receive(chunkData);

// remove unwanted data
byte[] validData = new byte[chunkData.position()];
System.arraycopy(chunkData.array(), 0, validData, 0, validData.length);

System.out.println("---has received data:" + new String(validData));