Deserialisation issue - java.io.StreamCorruptedException: invalid type code: 00

Question

I\'m writing a java file-transfer app, and i have some troubles with deserialisation myself-defined class Message from Datagramms.

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Answer 1

Are you sure you have received all of the bytes for the serialized objects? A DatagramSocket uses UDP under the hood. Are you sure that all of the packets have arrived?

Also, is it really a good idea to use UDP for transferring a serialized object? This is one case where TCP would seem to be more approriate. UDP does not guarantee delivery or delivery order which could easily cause a corrupted stream.

You should also really put a private static final long serialVersionUID = 1L; on your Message class.

Answer 2

receiveMSG = (Message) deserialize(receivedPacket.getData());

You need to change this to

receiveMSG = (Message) deserialize(receivedPacket.getData(), receivedPacket.getOffset(), receivedPacket.getLength);

and adjust your 'deserialise()' method accordingly, to accept 'offset' and 'length' parameters, and to use them when constructing the ByteArrayInputStream.

EDIT The code you posted doesn't compile: the expression that constructs the outgoing datagram packet is incorrect. It should be

new DatagramPacket(test, test.length, datagramSocket.getInetAddress(), datagramSocket.getPort())

I have no idea what packetOverhead is supposed to be, but you don't need it.

NB You don't need to create a new Message() the line before you call readObject().