DatagramPacket to string

问题

Trying to convert a received DatagramPacket to string, but I have a small problem. Not sure what's the best way to go about it.

The data I'll be receiving is mostly of unknown length, hence I have some buffer[1024] set on my receiving side. The problem is, suppose I sent string "abc" and the do the following on my receiver side...

buffer = new byte[1024]; 
packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
buffer = packet.getData();
System.out.println("Received: "+new String(buffer));

I get the following output: abc[][][][]][][][]..... all the way to the buffer length. I'm guessing all the junk/null at the end should've been ignored, so I must be doing something wrong." I know the buffer.length is the problem because if I change it to 3 (for this example), my out comes out just fine.

Thanks.

回答1:

new String(buffer, 0, packet.getLength())

回答2:

Using this code instead: String msg = new String(packet.getData(), packet.getOffset(), packet.getLength());

回答3:

The DatagramPacket's length field gives the length of the actual packet received. Refer to the javadoc for DatagramPacket.receive for more details.

So you simply need to use a different String constructor, passing the byte array and the actual received byte count.

See @jtahlborn or @GiangPhanThanhGiang's answers for example.

However, that still leaves the problem of which character encoding should be used when decoding the bytes into a UTF-16 string. For your particular example it probably doesn't matter. But it you are passing data that could include non-ASCII characters, then you need to decode using the correct charset. If you get that wrong, you are liable to get garbled characters in your String values.

回答4:

As I understand it, the DatagramPacket just has a bunch of junk at the end. As Stephen C. suggests, you might be able to find the actual length received. In that case, use:

int realSize = packet.getLength() //Method suggested by Stephen C.
byte[] realPacket = new byte[realSize];
System.arrayCopy(buffer, 0, realPacket, 0, realSize);

As for finding the length, I don't know.

回答5:

Try

System.out.println("Received: "+new String(buffer).trim());

String sentence = new String(packet.getData()).trim();
System.out.println("Received: "+sentence);

回答6:

Use this Code instead

buffer = new byte[1024]; 
packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
String data = new String(packet.getData());
System.out.println("Received: "+data);

来源：https://stackoverflow.com/questions/8557132/datagrampacket-to-string

标签

java

bytearray

datagram