Trying to send and receive message using protobuf in java,but got error: Protocol message contained an invalid tag (zero)

Question

The problem happened at server end, parseDelimitedFrom() calling.

Client End:

    C2SGainCard.Builder s = C2SGainCard.newBuilder();
    C2SGainCard c2s = s.build();

    GameRequest.Builder  reqBuilder=GameRequest.newBuilder();
    reqBuilder.setBody(c2s.toByteString());
    reqBuilder.setName(C2SGainCard.class.getSimpleName());
    reqBuilder.setPlayerId("3");
    GameRequest request=reqBuilder.build();

    DataOutputStream os = new DataOutputStream(socket.getOutputStream());
    os.write(request.toByteArray());
    os.flush();
    os.close();
    socket.close();

Server End:

    try{
        DataInputStream is = new DataInputStream(socket.getInputStream());
        GameRequest gameRequest = GameRequest.parseDelimitedFrom(is);
    }catch(Exception ex){
        System.out.println(ex.getMessage());
    }

And here is the another similar question:

Client End:

    C2SSell.Builder s = C2SSell.newBuilder();
    CardOnSell.Builder cardOnSell = CardOnSell.newBuilder();
    cardOnSell.setId(1);
    cardOnSell.setPlayerId(3);
    cardOnSell.setCardId(1);
    cardOnSell.setCurrentPrice(111);
    cardOnSell.setFixedPrice(555);
    cardOnSell.setDescription("cao");

    s.setCardOnSell(cardOnSell.build());

    C2SSell c2s = s.build(); 

socket processing was the same.

Server End:

    DataInputStream is = new DataInputStream(socket.getInputStream());
    byte[] b = new byte[1024];
    int len=is.read(b);
    String as = new String(b, 0, len);
    GameRequest gameRequest=GameRequest.parseFrom(as.getBytes());

Turns out that the server end will break at the parseFrom() calling again.But when I comment two lines:

cardOnSell.setCurrentPrice(111);
cardOnSell.setFixedPrice(555);

on the client End,the parseFrom() calling just worked without problem. At frist I suspected the .proto file has some problems and it's been proved there is no problem there... So how does this problem come? It that because I miss some data before the parseFrom() calling?

Answer 1

I can't remember exactly what format parseDelimitedFrom expects, but I suspect you just want parseFrom in your server side.

It's not clear why you're using os.write(request.toByteArray()) though, or indeed why you're creating a DataOutputStream. You should be able to use just OutputStream and InputStream, writing:

request.writeTo(socket.getOutputStream());

and then:

GameRequest gameRequest = GameRequest.parseFrom(socket.getInputStream());

If you do want the delimited version, you need to use writeDelimitedTo instead.