深入解析Android Socket源码：揭秘底

随着移动互联网的快速发展，Android系统作为全球最流行的移动操作系统，其内置的Socket通信机制在各个应用场景中扮演着至关重要的角色。Socket通信是网络编程的基础，它允许两个程序在不同的主机上进行数据交换。本文将深入解析Android Socket源码，带您了解其底层通信机制。

一、Socket概述

Socket是一种网络通信协议，它允许两个程序在不同的主机上进行数据交换。在Android系统中，Socket通信主要分为TCP和UDP两种类型。TCP（传输控制协议）是一种面向连接的、可靠的、基于字节流的传输层通信协议；UDP（用户数据报协议）是一种无连接的、不可靠的、基于数据报的传输层通信协议。

二、Android Socket源码解析

1.Socket类

在Android系统中，Socket类是进行Socket通信的主要类。下面以TCP Socket为例，分析其源码。

`java public class Socket implements Closeable { // ... 省略其他代码 ...

private static final String TAG = "Socket";
private final String mAddress;
private final int mPort;
private final boolean mReuseAddress;
private final int mSoTimeout;
private final boolean mKeepAlive;
private final boolean mTcpNoDelay;
private final boolean mLinger;
private final int mLingerSec;
private final int mSendBufferSize;
private final int mReceiveBufferSize;
private final boolean mUseKernelSockets;
private final boolean mUseLegacySocketImplementation;
private final boolean mIsConnected;
private final boolean mIsBound;
private final boolean mIsClosed;
private final boolean mIsSocketClosed;
private final boolean mIsSocketBound;
private final boolean mIsSocketConnected;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final boolean mIsSocketReceiveBufferSize;
private final boolean mIsSocketUseKernelSockets;
private final boolean mIsSocketUseLegacySocketImplementation;
private final boolean mIsSocketConnected;
private final boolean mIsSocketBound;
private final boolean mIsSocketClosed;
private final boolean mIsSocketError;
private final boolean mIsSocketTimeout;
private final boolean mIsSocketLinger;
private final boolean mIsSocketKeepAlive;
private final boolean mIsSocketTcpNoDelay;
private final boolean mIsSocketReuseAddress;
private final boolean mIsSocketSendBufferSize;
private final