WriteUTF和ReadUTF，我该如何写一个字符串并在另一侧得到一个简短的异常？

Question

Basically i'm doing a socket connection between two sides. A Java server and a Android client. I'm converting objects to String Json using Gson library , and sending them through method WriteUTF from Android client. But when i try to get response in Java server i get a "java.io.EOFException at java.io.DataInputStream.readUnsignedShort(Unknown Source)". How, if i didn't used this method (readUnsignedShort) or even didn't send any Short ? Here comes the codes.

Writing from Android client:

 try {
                DataInputStream in = new DataInputStream (s3.getInputStream());
                DataOutputStream out = new DataOutputStream(s3.getOutputStream());

                ap = (ArrayList<Produto>) InternalStorage.readObject(getBaseContext(),"pedido");

                 for(int i=0;i<ap.size()&& ap.size()>0;i++){

                        Produto p = new Produto("", "", 0f, "", "", 0);
                        p = ap.get(i);
                        Gson gson = new Gson();
                        String json = gson.toJson(p);
                        out.writeUTF(json);
                        out.flush();

                    }

And Reading from Java server:

try {
        // Get input from the client
        DataInputStream in = new DataInputStream (server.getInputStream());
        DataOutputStream out = new DataOutputStream(server.getOutputStream());


        while((line = in.readUTF()) != null) {
            boolean error = false;

            String json = line;
            Gson gson = new Gson();
            Produto p2 = gson.fromJson(json, Produto.class);
            c = dbDelegate.getCommandByNumber(p2.getMesa());
            p = dbDelegate.getProductByName(p2.getNome());
            if(c!=null && p!=null){
                error = false;
            inCommand.setCommand(c);
            inCommand.setDateAndTime(new Timestamp(System.currentTimeMillis()));
            inCommand.setProduct(p);
            inCommand.setLogin(FishingBoardFrameCashRegister.getInstance().getLogin());
            inCommand.setQuantity(p2.getQuantidade());
            inCommand.setPrice(String.valueOf((p2.getValor()*p2.getQuantidade())));
            inCommand.setObs(p2.getObs());
            inCommand.setProductName(p.getName());
            inCommand.setType(Product.ALL);
            inCommand.setSession(0);
            inCommand.setCommandSession(c.getSession());
            if(dbDelegate.insertProductInCommand(inCommand) == DbDelegate.CASH_CLOSED){
                error = true;
            }
            FishingBoardFrameCashRegister.getInstance().updateTable();
            }else{
                error = true;
            }

The log may help too:

trueIOException on socket listen: java.io.EOFException
java.io.EOFException
at java.io.DataInputStream.readUnsignedShort(Unknown Source)
at java.io.DataInputStream.readUTF(Unknown Source)
at com.keymax.server.doComms3.run(Server3.java:71)

Server3.java:71 is this line in server code: while((line = in.readUTF()) != null) {

Answer 1

I think the EOFException is expected here, because that's what you will get if you call readUTF and there is no data left.

I would fix this by using writeInt before the loop to write out how many strings are about to be written, and then readInt on the other end, so that you don't call readUTF more times than the number of strings actually available in the stream.

writeUTF probably writes the length of the string and then the data in the string, which explains why readUnsignedShort is the one getting the EOFException .