实现流程：

服务端

package com.jzj.socket;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;


public abstract class SocketTransceiver implements Runnable {

	protected Socket socket;
	protected InetAddress addr;
	protected DataInputStream in;
	protected DataOutputStream out;
	private boolean runFlag;

	
	public SocketTransceiver(Socket socket) {
		this.socket = socket;
		this.addr = socket.getInetAddress();
	}

	
	public InetAddress getInetAddress() {
		return addr;
	}

	
	public void start() {
		runFlag = true;
		new Thread(this).start();
	}

	
	public void stop() {
		runFlag = false;
		try {
			socket.shutdownInput();
			in.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	
	public boolean send(String s) {
		if (out != null) {
			try {
				out.writeUTF(s);
				out.flush();
				return true;
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return false;
	}

	
	@Override
	public void run() {
		try {
			in = new DataInputStream(this.socket.getInputStream());
			out = new DataOutputStream(this.socket.getOutputStream());
		} catch (IOException e) {
			e.printStackTrace();
			runFlag = false;
		}
		while (runFlag) {
			try {
				final String s = in.readUTF();
				this.onReceive(addr, s);
			} catch (IOException e) {
				// 连接被断开(被动)
				runFlag = false;
			}
		}
		// 断开连接
		try {
			in.close();
			out.close();
			socket.close();
			in = null;
			out = null;
			socket = null;
		} catch (IOException e) {
			e.printStackTrace();
		}
		this.onDisconnect(addr);
	}

	
	public abstract void onReceive(InetAddress addr, String s);

	
	public abstract void onDisconnect(InetAddress addr);
}

 TCP连接工具类

package com.jzj.socket;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;


public abstract class TcpServer implements Runnable {

	private int port;
	private boolean runFlag;
	private List<SocketTransceiver> clients = new ArrayList<SocketTransceiver>();

	
	public TcpServer(int port) {
		this.port = port;
	}

	
	public void start() {
		runFlag = true;
		new Thread(this).start();
	}

	
	public void stop() {
		runFlag = false;
	}

	
	@Override
	public void run() {
		try {
			final ServerSocket server = new ServerSocket(port);
			while (runFlag) {
				try {
					final Socket socket = server.accept();
					startClient(socket);
				} catch (IOException e) {
					// 接受客户端连接出错
					e.printStackTrace();
					this.onConnectFailed();
				}
			}
			// 停止服务器，断开与每个客户端的连接
			try {
				for (SocketTransceiver client : clients) {
					client.stop();
				}
				clients.clear();
				server.close();
			} catch (Exception e) {
				e.printStackTrace();
			}
		} catch (IOException e) {
			// ServerSocket对象创建出错，服务器启动失败
			e.printStackTrace();
		}
		this.onServerStop();
	}

	
	private void startClient(final Socket socket) {
		SocketTransceiver client = new SocketTransceiver(socket) {

			@Override
			public void onReceive(InetAddress addr, String s) {
				TcpServer.this.onReceive(this, s);
			}

			@Override
			public void onDisconnect(InetAddress addr) {
				clients.remove(this);
				TcpServer.this.onDisconnect(this);
			}
		};
		client.start();
		clients.add(client);
		this.onConnect(client);
	}

	
	public abstract void onConnect(SocketTransceiver client);

	
	public abstract void onConnectFailed();

	
	public abstract void onReceive(SocketTransceiver client, String s);

	
	public abstract void onDisconnect(SocketTransceiver client);

	
	public abstract void onServerStop();
}

测试类：

package com.jzj.socket;

public class ClsMainServer {

	public static void main(String[] args) {
		int port = 1234;
		TcpServer server = new TcpServer(port) {

			@Override
			public void onConnect(SocketTransceiver client) {
				printInfo(client, "Connect");
			}

			@Override
			public void onConnectFailed() {
				System.out.println("Client Connect Failed");
			}

			@Override
			public void onReceive(SocketTransceiver client, String s) {
				printInfo(client, "Send Data: " + s);
				if(s.equals("天王盖地虎")){
					client.send("小鸡炖蘑菇"+"\n");
				}else if(s.equals("有朋自远方来")){
					client.send("必诛之"+"\n");
				}else if(s.equals("芝麻开门")){
					client.send("不开就不开"+"\n");
				}else {
					s = s.replace("吗","");
					s = s.replace("?","!");
					s = s.replace("？","!");
					client.send(s+"\n");
				}

			}

			@Override
			public void onDisconnect(SocketTransceiver client) {
				printInfo(client, "Disconnect");
			}

			@Override
			public void onServerStop() {
				System.out.println("--------Server Stopped--------");
			}
		};
		System.out.println("--------Server Started--------");
		server.start();
	}

	static void printInfo(SocketTransceiver st, String msg) {
		System.out.println("Client " + st.getInetAddress().getHostAddress());
		System.out.println("  " + msg);
	}
}

安卓端；

package com.jzj.socket;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;


public abstract class SocketTransceiver implements Runnable {

	protected Socket socket;
	protected InetAddress addr;
	protected DataInputStream in;
	protected DataOutputStream out;
	private boolean runFlag;

	
	public SocketTransceiver(Socket socket) {
		this.socket = socket;
		this.addr = socket.getInetAddress();
	}

	
	public InetAddress getInetAddress() {
		return addr;
	}

	
	public void start() {
		runFlag = true;
		new Thread(this).start();
	}

	
	public void stop() {
		runFlag = false;
		try {
			socket.shutdownInput();
			in.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	
	public boolean send(String s) {
		if (out != null) {
			try {
				out.writeUTF(s);
				out.flush();
				return true;
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return false;
	}

	
	@Override
	public void run() {
		try {
			in = new DataInputStream(this.socket.getInputStream());
			out = new DataOutputStream(this.socket.getOutputStream());
		} catch (IOException e) {
			e.printStackTrace();
			runFlag = false;
		}
		while (runFlag) {
			try {
				final String s = in.readUTF();
				this.onReceive(addr, s);
			} catch (IOException e) {
				// 连接被断开(被动)
				runFlag = false;
			}
		}
		// 断开连接
		try {
			in.close();
			out.close();
			socket.close();
			in = null;
			out = null;
			socket = null;
		} catch (IOException e) {
			e.printStackTrace();
		}
		this.onDisconnect(addr);
	}

	
	public abstract void onReceive(InetAddress addr, String s);

	
	public abstract void onDisconnect(InetAddress addr);
}

package com.jzj.socket;

import java.net.InetAddress;
import java.net.Socket;


public abstract class TcpClient implements Runnable {

	private int port;
	private String hostIP;
	private boolean connect = false;
	private SocketTransceiver transceiver;

	
	public void connect(String hostIP, int port) {
		this.hostIP = hostIP;
		this.port = port;
		new Thread(this).start();
	}

	@Override
	public void run() {
		try {
			Socket socket = new Socket(hostIP, port);
			transceiver = new SocketTransceiver(socket) {

				@Override
				public void onReceive(InetAddress addr, String s) {
					TcpClient.this.onReceive(this, s);
				}

				@Override
				public void onDisconnect(InetAddress addr) {
					connect = false;
					TcpClient.this.onDisconnect(this);
				}
			};
			transceiver.start();
			connect = true;
			this.onConnect(transceiver);
		} catch (Exception e) {
			e.printStackTrace();
			this.onConnectFailed();
		}
	}

	
	public void disconnect() {
		if (transceiver != null) {
			transceiver.stop();
			transceiver = null;
		}
	}

	
	public boolean isConnected() {
		return connect;
	}

	
	public SocketTransceiver getTransceiver() {
		return isConnected() ? transceiver : null;
	}

	
	public abstract void onConnect(SocketTransceiver transceiver);

	
	public abstract void onConnectFailed();

	
	public abstract void onReceive(SocketTransceiver transceiver, String s);

	
	public abstract void onDisconnect(SocketTransceiver transceiver);
}

package com.demo.main;

import com.jzj.socket.SocketTransceiver;
import com.jzj.socket.TcpClient;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

	private Button bnConnect;
	private TextView txReceive;
	private EditText edIP, edPort, edData;

	private Handler handler = new Handler(Looper.getMainLooper());

	private TcpClient client = new TcpClient() {

		@Override
		public void onConnect(SocketTransceiver transceiver) {
			refreshUI(true);
		}

		@Override
		public void onDisconnect(SocketTransceiver transceiver) {
			refreshUI(false);
		}

		@Override
		public void onConnectFailed() {
			handler.post(new Runnable() {
				@Override
				public void run() {
					Toast.makeText(MainActivity.this, "连接失败",
							Toast.LENGTH_SHORT).show();
				}
			});
		}

		@Override
		public void onReceive(SocketTransceiver transceiver, final String s) {
			handler.post(new Runnable() {
				@Override
				public void run() {
					txReceive.append(s);
				}
			});
		}
	};

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		this.findViewById(R.id.bn_send).setOnClickListener(this);
		bnConnect = (Button) this.findViewById(R.id.bn_connect);
		bnConnect.setOnClickListener(this);

		edIP = (EditText) this.findViewById(R.id.ed_ip);
		edPort = (EditText) this.findViewById(R.id.ed_port);
		edData = (EditText) this.findViewById(R.id.ed_dat);
		txReceive = (TextView) this.findViewById(R.id.tx_receive);
		txReceive.setOnClickListener(this);

		refreshUI(false);
	}

	@Override
	public void onStop() {
		client.disconnect();
		super.onStop();
	}

	@Override
	public void onClick(View v) {
		switch (v.getId()) {
		case R.id.bn_connect:
			connect();
			break;
		case R.id.bn_send:
			sendStr();
			break;
		case R.id.tx_receive:
			clear();
			break;
		}
	}

	
	private void refreshUI(final boolean isConnected) {
		handler.post(new Runnable() {
			@Override
			public void run() {
				edPort.setEnabled(!isConnected);
				edIP.setEnabled(!isConnected);
				bnConnect.setText(isConnected ? "断开" : "连接");
			}
		});
	}

	
	private void connect() {
		if (client.isConnected()) {
			// 断开连接
			client.disconnect();
		} else {
			try {
				String hostIP = edIP.getText().toString();
				int port = Integer.parseInt(edPort.getText().toString());
				client.connect(hostIP, port);
			} catch (NumberFormatException e) {
				Toast.makeText(this, "端口错误", Toast.LENGTH_SHORT).show();
				e.printStackTrace();
			}
		}
	}

	
	private void sendStr() {
		try {
			String data = edData.getText().toString();
			client.getTransceiver().send(data);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	
	private void clear() {
		new AlertDialog.Builder(this).setTitle("确认清除?")
				.setNegativeButton("取消", null)
				.setPositiveButton("确认", new DialogInterface.OnClickListener() {
					@Override
					public void onClick(DialogInterface dialog, int which) {
						txReceive.setText("");
					}
				}).show();
	}
}

服务端源码

安卓端源码