How to send message to device on local network using Java/Kotlin sockets?-CodePudding

I need to send a message (in JSON format) to a IoT device connected on my local network. The device is a smart bulb that I would like to toggle at every request. I know the IP address and the port of the device.

I am already able to control it using a Python script, like so:

request = """{"id":1,"method":"toggle","params":["smooth",300]}\r\n""".encode("utf8")
    
print(request) # Prints: b'{"id":1,"method":"toggle","params":["smooth",300]}\r\n'
    
_socket= socket.socket(socket.AF_INET, socket.SOCK_STREAM)
_socket.settimeout(5)
_socket.connect(('123.456.7.89', 12345))
_socket.send(request)

But I need to run it using Java/Kotlin. I tried converting the code, and so far I got this (in Kotlin):

val request = """{"id":0,"method":"toggle","params":["smooth",300]}\r\n""".encodeUtf8().toByteArray()
    
println(String(request, Charsets.UTF_8)) // Prints: {"id":0,"method":"toggle","params":["smooth",300]}\r\n
    
val socket = Socket()
val socketAddress = InetSocketAddress("123.456.7.89", 12345)
socket.connect(socketAddress, 5_000)
socket.getOutputStream().write(request)

This script runs without any exception, but it also doesn't work, and I couldn't find a way to proceed from here.

CodePudding user response：

In Java you can do it as following:

public class Client {

    public static final String LOCALHOST = "localhost"; // Example host
    public static final int PORT = 1234;                // Example port

    public static void main(String[] args) throws IOException {
        try (Socket socket = new Socket(LOCALHOST, PORT)) {
            System.out.println("Connected to Server!");
            BufferedWriter socketWriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), StandardCharsets.UTF_8));
            socketWriter.write("{\"id\":1,\"method\":\"toggle\",\"params\":[\"smooth\",300]}\n");
            socketWriter.close();
        }
        System.out.println("Disconnected from server");
    }
}

In case you have a JDK 15 you can use the new text block feature to write the String:

/*socketWriter.write("""
    {"id":1,"method":"toggle","params":["smooth",300]}
    """);*/