你的主机中的软件中止了一个已建立的连接。

【错误一】
Caused by: java.io.IOException: 你的主机中的软件中止了一个已建立的连接。
at sun.nio.ch.SocketDispatcher.write0(Native Method)
at sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:51)
at sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:93)
at sun.nio.ch.IOUtil.write(IOUtil.java:65)
at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:471)
at org.apache.tomcat.util.net.NioChannel.write(NioChannel.java:125)
at org.apache.tomcat.util.net.NioSelectorPool.write(NioSelectorPool.java:185)
at org.apache.coyote.http11.upgrade.NioServletOutputStream.doWriteInternal(NioServletOutputStream.java:94)
at org.apache.coyote.http11.upgrade.NioServletOutputStream.doWrite(NioServletOutputStream.java:61)
at org.apache.coyote.http11.upgrade.AbstractServletOutputStream.writeInternal(AbstractServletOutputStream.java:153)
at org.apache.coyote.http11.upgrade.AbstractServletOutputStream.write(AbstractServletOutputStream.java:121)
at org.apache.tomcat.websocket.server.WsRemoteEndpointImplServer.onWritePossible(WsRemoteEndpointImplServer.java:94)
at org.apache.tomcat.websocket.server.WsRemoteEndpointImplServer.doWrite(WsRemoteEndpointImplServer.java:81)
at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.writeMessagePart(WsRemoteEndpointImplBase.java:456)
at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.startMessage(WsRemoteEndpointImplBase.java:344)
at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.startMessageBlock(WsRemoteEndpointImplBase.java:276)
... 16 more

【错误二】
The WebSocket session [0] has been closed and no method (apart from close()) may be called on a closed session

【解决办法】
if(!s.session.isOpen()){
System.out.println("s.session为空----------------");
}else{
System.out.println("session.getBasicRemote()=="+s.session.getBasicRemote());
s.session.getBasicRemote().sendText(user.getName()+","+user.getPhoto());
}