Socket编程就是根据服务器/客户端模型，在Socket API的基础上开发的网络计算机和进程间相互通信的应用。
1.服务端绑定一个端口号，并在此端口监听客户端的连接，线程会block直到有客户连接请求，读取请求信息，然后处理并返回。
2.客户端和指定的服务器的指定端口建立连接，发送请求信息，并等待返回信息。
服务端：
package com.bijian.study01;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class MyServer {
ServerSocket server;
Socket client;
BufferedReader in;
PrintWriter out;
public MyServer() {
try {
// Instantiate a ServerSocket with specified port
server = new ServerSocket(4451);
// Listen on the port to receive the connection request
client = server.accept();
// Construct a reader to get the information from the client
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
// Construct a writer to respond to the client
out = new PrintWriter(client.getOutputStream());
// Continually to retrieve the message from the client
while (true) {
String input = in.readLine();
System.out.println(input);
out.println("has received: " + input);
out.flush();
if (input.equals("end"))
break;
}
} catch (IOException ex) {
ex.printStackTrace();
} finally {
// Release the resources - omitted
}
}
public static void main(String[] args) {
new MyServer();
}
}
客户端：
package com.bijian.study01;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class MyClient {
Socket connection;
BufferedReader in;
PrintWriter out;
BufferedReader reader;
public MyClient() {
try {
// Establish a connection to the Socket server
connection = new Socket(InetAddress.getLocalHost(), 4451);
// Construct a reader to get the response from the server
in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
// Construct a writer to send messages to the server
out = new PrintWriter(connection.getOutputStream());
// Construct a reader to accept the user input
reader = new BufferedReader(new InputStreamReader(System.in));
// Continuously send out the messages to the server and receive the response
while (true) {
String str = reader.readLine();
out.println(str);
out.flush();
System.out.println("sent out: " + str);
if (str.equals("end"))
break;
System.out.println(in.readLine());
}
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// Release the resources - omitted
}
}
public static void main(String[] args) {
new MyClient();
}
}
测试运行结果：
客户端：
hello sent out: hello has received: hello today sent out: today has received: today bye sent out: bye has received: bye end sent out: end
服务端：
hello today bye end
其中：
1.out = new PrintWriter(connection.getOutputStream()); 使用系统默认的编码格式。
如果默认编码不符合要求，使用OutputStreamWriter指定：
out = new PrintWriter(new OutputStreamWriter(connection.getOutputStream(), "utf-8"));
2.可以把手动flush改成自动的：
out = new PrintWriter(connection.getOutputStream(), true);
这样，当println, printf, format方法调用时，将缓存输出到底层流并清空缓存。
3.必须首先开启服务端，否则客户端建立连接的时候会报java.net.ConnectException: Connection refused: connect