继承关系
java.nio.channels.Channel
A channel represents an open connection to an entity such as a hardware device, a file, a network socket, or a program component that is capable of performing one or more distinct I/O operations, for example reading or writing.
public abstract SocketChannel accept() throws IOException;The socket channel for the new connection,
or null if this channel is in non-blocking mode
and no connection is available to be accepted
