我怎么知道客户端在套接字中发送FIN包？

Question

In client, when call clent.close() , it will send a FIN packet to try to end the connection. Are there any API for server side to know there comes a FIN packet to close the connection in server side? If not, why? What's the best pratice to close connection in both side?

Client code:

    String host = "127.0.0.1"; 
    int port = 8899;
    Socket client = new Socket(host, port);
    String data = "Hello world";
    Writer writer = new OutputStreamWriter(client.getOutputStream());
    writer.write(data);
    writer.flush();
    writer.close();
    client.close();

A example can be seen here .

Answer 1

When the server receives a FIN, it will treat this as the end-of-stream condition.

In other words, every time you call read on the socket's InputStream, it will return -1 instead of reading any data - the same as if you were reading from a file and you got to the end of the file.

Answer 2

When the peer receives a FIN:

• read() will return -1
• readLine() will return null
• readXXX() will throw EOFException for any other X.

What won't happen:

• Socket.isClosed() won't magically become true
• Socket.isConnected() won't magically become false.