Java套接字客户端未接收到数据

Question

I seem to be having a few issues working with sockets in Java. The issue is that the client doesn't receive data and, when it does sometimes receive it, the data is delayed by a large amount of time. The server receives all data from the client correctly and responds how I would like it to (at least from the output it does). Any help on this would be helpful.

Server:

try{
        ServerSocket server = new ServerSocket(6969);
        while (true){
            System.out.println("Listening on port 6969");
            Socket client = server.accept();
            System.out.println("Accepted");
            BufferedReader input = new BufferedReader(new InputStreamReader(client.getInputStream()));
            System.out.println("Got the input reader");

            //This is where the input data will be stored
            StringBuffer sb = new StringBuffer();
            while (input.ready()){
                System.out.println("Reading data");
                int cha = input.read();
                if ((cha < 0)){
                    break;
                }
                sb.append((char)cha);
            }

            System.out.println("Recived Data:" + sb.toString());
            BufferedWriter output = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
            System.out.println(sb.toString().equalsIgnoreCase("INIT"));
            if (sb.toString().equalsIgnoreCase("INIT")){
                JSONObject jo = new JSONObject();
                jo.put("password", "Password123");
                jo.put("testString", "tESTsTRING");
                jo.put("intTest", 222);
                System.out.println("Sending data:" + jo.toString());
                output.write(jo.toString());
                output.flush();
            }

        }
    }catch (Exception e){
        System.out.println(e.getMessage());
    }

Client:

try{
        Socket connection = new Socket(host, 6969);
        System.out.println("Set up connection. Sending data and waiting for response");
        BufferedWriter output = new BufferedWriter(new OutputStreamWriter(connection.getOutputStream()));

        output.write("INIT");
        output.flush();

        BufferedReader input = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        System.out.println("Got the input reader: " + connection.getInputStream().available());

        //This is where the input data will be stored
        StringBuffer sb = new StringBuffer();
        System.out.println(input.readLine() + " :: " + input.ready());
        while (input.ready()){
            System.out.println("Reading data");
            int cha = input.read();
            if ((cha < 0)){
                break;
            }
            sb.append((char)cha);
        }

        System.out.println("Recived Data:" + sb.toString());

    }catch (Exception e){
        e.printStackTrace();
    }

The server console output:

Listening on port 6969
Accepted
Got the input reader
Reading data
Reading data
Reading data
Reading data
Recived Data:INIT
true
Sending data:{"intTest":222,"testString":"tESTsTRING","password":"Password123"}

The client output:

Set up connection. Sending data and waiting for response
Got the input reader: 0

Also, the server sometimes doesn't receive the data from the client even though it recognizes that the client is trying to send the data.

Answer 1

If you don't "nicely" close a socket, the other side won't notice and keeps waiting for data. That's why you have to really think about what you do with exceptions here and when to block and for how long. A lost connection can only be discovered when it throws an IOException on next attempt to read or write. "next" in the sense of attempt started after connection has been lost.

This answer is not nearly covering everything, but I hope this will give you some hints.