Serversocket and Socket

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I’m trying to create a ServerSocket:

public class RunServer {

public static void main(String[] args) {
    try {

        byte[] buffer = new byte[1024];
        String passwordCript;

        ServerSocket socketRecepcao = new ServerSocket(22300);
        System.out.println("Servidor esperando conexão na porta 22300");

        while (true) {

            Socket socketConexao = socketRecepcao.accept();
            System.out.println("Conexão estabelecida na porta "
                    + socketConexao.getPort());

            InputStream is = socketConexao.getInputStream();
            OutputStream os = socketConexao.getOutputStream();

            is.read(buffer);

            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(buffer, 0, buffer.length);

            BigInteger hash = new BigInteger(1, md.digest());
            passwordCript = hash.toString(16);

            buffer = passwordCript.getBytes();
            os.write(buffer);

            socketConexao.close();
        }

    } catch (NoSuchAlgorithmException e) {

        e.printStackTrace();

    } catch (IOException e) {

        e.printStackTrace();

    }
}

NOTE: It’s a simple code to create ServerSocket,

But I get this exception:

java.net.BindException: Address already in use: JVM_Bind
    at java.net.DualStackPlainSocketImpl.bind0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketBind(Unknown Source)
    at java.net.AbstractPlainSocketImpl.bind(Unknown Source)
    at java.net.PlainSocketImpl.bind(Unknown Source)
    at java.net.ServerSocket.bind(Unknown Source)
    at java.net.ServerSocket.<init>(Unknown Source)
    at java.net.ServerSocket.<init>(Unknown Source)
    at com.iamExport.RunServer.main(RunServer.java:20)
  1. Why is this exception being cast?
  2. What care should I take after the ServerSocket work?

NOTE: I know there are other types of connection like API HttpClient, etc., but I am studying socket...

java socket md5

  • Using Eclipse? Check the Console for multiple instances of the running program.

  • @utluiz, I checked, it’s actually right. I ended up running the Serversocket it went into background... Thank you guys. I am wrong to believe that I need a method to verify that a particular port can be used?

  • Eduardo, put a pad try/catch to handle the exceptions to return the call to the method accept() and in the event of falling into a catch with BindException, shows a more specific message like "port in use".

  • @utluiz, I’ll do it.

1 answer

5


Basically, there is already something listening on this door (22300). Possibly your own program, running in the background -- take a look at the java processes, make sure to kill them all, and try again.

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