什么是Android上正确的TCP / IP套接字关闭顺序？

Question

i have some code that does send a message using tcp/ip.

the client sequence is: connect, write, flush, shutdown output, shutdown input, close socket.

the server sequence is accept, readline, shutdown input, shutdown output, close socket.

this works fine on windows using the same wifi betwork as the android. on a 2013 nexus 7 android 6.0.1, the socket.shutdownInput() sometimes throws an ENOTCONN (please see below). the program still works, but i would like to understand what is happening and get rid of the exception if possible.

thanks

edit: closing the output stream (and not doing a shutdown output) works better.

01-29 23:24:29.394 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err: java.net.SocketException: shutdown failed: ENOTCONN (Transport endpoint is not connected)
01-29 23:24:29.394 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.net.PlainSocketImpl.shutdownInput(PlainSocketImpl.java:361)
01-29 23:24:29.394 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.net.Socket.shutdownInput(Socket.java:635)
01-29 23:24:29.394 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at com.tayek.tablet.io.Client.send(Client.java:49)
01-29 23:24:29.394 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at com.tayek.tablet.Tablet.send(Tablet.java:66)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at com.tayek.tablet.Tablet.access$200(Tablet.java:11)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at com.tayek.tablet.Tablet$SendCallable.call(Tablet.java:82)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at com.tayek.tablet.Tablet$SendCallable.call(Tablet.java:72)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
01-29 23:24:29.395 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.lang.Thread.run(Thread.java:818)
01-29 23:24:29.397 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err: Caused by: android.system.ErrnoException: shutdown failed: ENOTCONN (Transport endpoint is not connected)
01-29 23:24:29.397 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at libcore.io.Posix.shutdown(Native Method)
01-29 23:24:29.397 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at libcore.io.ForwardingOs.shutdown(ForwardingOs.java:159)
01-29 23:24:29.397 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     at java.net.PlainSocketImpl.shutdownInput(PlainSocketImpl.java:359)
01-29 23:24:29.397 7164-9300/com.tayek.tablet.gui.android.cb7 W/System.err:     ... 10 more

Answer 1

connect, write, flush,

Flush before close is redundant.

shutdown output, shutdown input, close socket

Both shutdowns are redundant before close.

All you need is connect, write, close.