Socket通常也称作“套接字”，用于描述IP地址和端口，可以用来实现不同虚拟机或不同计算机之间的通信。百度百科
套接字允许应用程序插入到网络中，并与插入到网络中的其他应用程序通信。《TCP/IP Socket编程·TCP/IP in C》
Socket编程示意图：
服务器需要先启动，等待客户端连接。客户端主动连接服务器，连接成功才能通信。
import java.net.*;import java.io.*;public class Skt字节流S {public static void main(String args) {try {ServerSocket sSocket = new ServerSocket(8888);System.out.println(“new ServerSocket”);Socket s = sSocket.accept;System.out.println(“accept”);InputStream is = s.getInputStream;OutputStream os = s.getOutputStream;byte b = new byte[1024];int len = is.read(b);String str = new String(b, 0, len);System.out.println(“客户端说：” + str);os.write(“对不起，我们这三碗不过岗”.getBytes);is.close;os.close;s.close;sSocket.close;System.out.println(“服务器端，OVER”);} catch (Exception e) }}客户端：
import java.net.*;import java.io.*;public class Skt字节流C {public static void main(String args) {try {// Socket s = new Socket(InetAddress.getLocalHost , 8888);Socket s = new Socket(“127.0.0.1”, 8888);InputStream is = s.getInputStream;OutputStream os = s.getOutputStream;os.write(“你好，我要10碗酒，三斤牛肉”.getBytes);byte b = new byte[1024];int len = -1;while ((len = is.read(b)) > 0) {String str = new String(b, 0, len);System.out.println(“服务器端的回复：” + str);}is.close;os.close;s.close;System.out.println(“客户端Over”);} catch (UnknownHostException e) {e.printStackTrace;} catch (IOException e) {e.printStackTrace;}}}看效果时，可以一个程序用Eclipse启动，一个用cmd启动，编译时如果有错，可用如下语句：
javac -encoding utf-8 XXX.javacmd运行程序时，不要有包名。
import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.PrintWriter;import java.net.ServerSocket;import java.net.Socket;public class SktCharacterS {public static void main(String args) {try {ServerSocket sSocket = new ServerSocket(8888);Socket s = sSocket.accept;InputStream is = s.getInputStream;OutputStream os = s.getOutputStream;InputStreamReader isr = new InputStreamReader(is);BufferedReader bufR = new BufferedReader(isr);PrintWriter prtW = new PrintWriter(os);// String str = bufR.readLine;System.out.println(“” + str);prtW.print(“你好，我是服务器”);prtW.flush;bufR.close;isr.close;is.close;prtW.close;os.close;s.close;sSocket.close;} catch (IOException e) {e.printStackTrace;}}}客户端：
import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.PrintWriter;import java.net.InetAddress;import java.net.Socket;import java.net.UnknownHostException;public class SktCharacterC {public static void main(String args) {Socket s;try {s = new Socket(InetAddress.getLocalHost, 8888);InputStream is = s.getInputStream;OutputStream os = s.getOutputStream;PrintWriter prtW = new PrintWriter(os);InputStreamReader isr = new InputStreamReader(is);BufferedReader bufR = new BufferedReader(isr);// -prtW.println(“你好我是客户机”);prtW.flush;String str = bufR.readLine;System.out.println(“” + str);bufR.close;isr.close;is.close;prtW.close;os.close;s.close;} catch (UnknownHostException e) {e.printStackTrace;} catch (IOException e) {e.printStackTrace;}}}socket发送文件(基本款)服务端：
import java.net.*;import java.io.*;public class SktFileS {public static void main(String args) {try {ServerSocket sSocket = new ServerSocket(8888);Socket s = sSocket.accept;InputStream ips = s.getInputStream;FileOutputStream fos = new FileOutputStream(“recv.png”);byte b = new byte[1024];int nLen = -1;while (true) {nLen = ips.read(b);if (nLen == -1) {break;}fos.write(b, 0, nLen);}fos.close;ips.close;s.close;sSocket.close;} catch (Exception e) finally {System.out.println(“服务器端，OVER”);}}}客户端：
import java.net.*;import java.io.*;public class SktFileC {public static void main(String args) {try {Socket s = new Socket(“127.0.0.1”, 8888);OutputStream ops =
