ServerSocket 类的一个对象表示Java中的TCP服务器套接字。
ServerSocket 对象可以接受来自远程客户端的连接请求。
我们可以使用no-args构造函数创建一个未绑定的服务器套接字，并使用其bind()方法将其绑定到本地端口和本地IP地址。
以下代码显示如何创建服务器套接字：
import java.net.InetSocketAddress;
import java.net.ServerSocket;
public class Main {
public static void main(String[] argv) throws Exception {
// Create an unbound server socket
ServerSocket serverSocket = new ServerSocket();
// Create a socket address object
InetSocketAddress endPoint = new InetSocketAddress("localhost", 12900);
// Set the wait queue size to 100
int waitQueueSize = 100;
// Bind the server socket to localhost and at port 12900 with
// a wait queue size of 100
serverSocket.bind(endPoint, waitQueueSize);
}
}
您可以通过使用以下任何构造函数在一个步骤中组合create，bind和listen操作。
等待队列大小的默认值为50。
本地IP地址的缺省值是通配符地址，即服务器计算机的所有IP地址。
ServerSocket(int port)
ServerSocket(int port, int waitQueueSize)
ServerSocket(int port, int waitQueueSize, InetAddress bindAddr)
您可以将套接字创建和绑定步骤合并为一个语句。
以下代码显示如何在端口12900创建服务器套接字，其中100作为等待队列大小，并在localhost回送地址。
ServerSocket serverSocket = new ServerSocket(12900, 100, InetAddress.getByName("localhost")); 要接受远程连接请求，请调用服务器套接字上的accept()方法。
accept()方法调用阻塞执行，直到来自远程客户端的请求到达其等待队列。
The following code calls on ServerSocket will wait for a new remote connection request.
Socket activeSocket = serverSocket.accept();
Socket类包含两个方法getInputStream()和getOutputStream()用于读取和写入连接的套接字。
BufferedReader br = new BufferedReader(new InputStreamReader(activeSocket.getInputStream()));
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(activeSocket.getOutputStream()));
String s = br.readLine();
bw.write("hello");
bw.flush();
最后，使用套接字的close()方法关闭连接。关闭套接字还会关闭其输入和输出流。
activeSocket.close();
以下代码显示如何创建服务器套接字。
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
public class Main {
public static void main(String[] args) throws Exception {
ServerSocket serverSocket = new ServerSocket(12900, 100,
InetAddress.getByName("localhost"));
System.out.println("Server started at: " + serverSocket);
while (true) {
System.out.println("Waiting for a connection...");
final Socket activeSocket = serverSocket.accept();
System.out.println("Received a connection from " + activeSocket);
Runnable runnable = () -> handleClientRequest(activeSocket);
new Thread(runnable).start(); // start a new thread
}
}
public static void handleClientRequest(Socket socket) {
try{
BufferedReader socketReader = null;
BufferedWriter socketWriter = null;
socketReader = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
socketWriter = new BufferedWriter(new OutputStreamWriter(
socket.getOutputStream()));
String inMsg = null;
while ((inMsg = socketReader.readLine()) != null) {
System.out.println("Received from client: " + inMsg);
String outMsg = inMsg;
socketWriter.write(outMsg);
socketWriter.write("\n");
socketWriter.flush();
}
socket.close();
}catch(Exception e){
e.printStackTrace();
}
}
}