在Java中，套接字实现类为SocketImpl（抽象基类），包含所有的套接字通信方法。
编程接口为ServerSocket（服务器）和Socket（客户端），内含SocketImpl实例，根据角色调用真正的套接字方法。
- SocketImpl
// 创建套接字：流式/数据报
void create(boolean stream);
// 绑定本地IP地址和端口
void bind(InetAddress host, int port);
// 监听请求
void listen(int backlog);
// 请求连接
void connect(InetAddress address, int port);
// 接受连接
void accept(SocketImpl s);
// 通过输出流发送消息
OutputStream getOutputStream();
void shutdownOutput();
// 通过输入流读取消息
InputStream getInputStream();
void shutdownInput();
// 关闭套接字
void close();
- ServerSocket
// 创建套接字、绑定本地端口、监听连接请求
ServerSocket(int port);
// 阻塞直到建立连接
// 返回：与客户端通信的Socket实例
Socket accept();
// 关闭套接字
void close();
- Socket
// 创建套接字、请求远程套接字，阻塞直到建立连接
Socket(String host, int port)
// 通过输出流发送消息
OutputStream getOutputStream();
// 关闭发送
void shutdownOutput();
// 通过输入流读取消息
InputStream getInputStream();
// 关闭读取
void shutdownInput();
// 关闭套接字
void close();
-
示例代码：
- 服务器：
int port = 8000;
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(port);
System.out.println("服务器监听：" + port);
for (int i = 0; i < 3; i++) {
Socket socket = serverSocket.accept();
System.out.println("\n服务器建立连接：" +
"本地（" + socket.getLocalAddress().getHostAddress() + ":" + socket.getLocalPort() + "），" +
"远程（" + socket.getInetAddress().getHostAddress() + ":" + socket.getPort() + "）");
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));
String line = reader.readLine();
System.out.println("他：" + line);
line = "你好，我是服务器！\n";
System.out.print("我：" + line);
writer.write(line);
writer.flush();
while (true) {
line = reader.readLine();
if (line == null) {
break;
}
System.out.println("他：" + line);
}
socket.shutdownInput();
line = "再见，客户端！\n";
System.out.print("我：" + line);
writer.write(line);
writer.flush();
socket.shutdownOutput();
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (serverSocket != null) {
try {
serverSocket.close();
System.out.println("\n服务器关闭");
} catch (IOException e) {
e.printStackTrace();
}
}
}
- 客户端：
String host = "127.0.0.1";
int port = 8000;
Socket socket = null;
try {
socket = new Socket();
socket.connect(new InetSocketAddress(host, port));
System.out.println("客户端建立连接：" +
"本地（" + socket.getLocalAddress().getHostAddress() + ":" + socket.getLocalPort() + "），" +
"远程（" + socket.getInetAddress().getHostAddress() + ":" + socket.getPort() + "）");
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF-8"));
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));
String line = "你好，我是客户端！\n";
System.out.print("我：" + line);
writer.write(line);
writer.flush();
line = reader.readLine();
System.out.println("他：" + line);
for (int i = 1; i <= 3; i++) {
line = "第" + i + "句。\n";
System.out.print("我：" + line);
writer.write(line);
writer.flush();
}
line = "再见，服务器！\n";
System.out.print("我：" + line);
writer.write(line);
writer.flush();
socket.shutdownOutput();
line = reader.readLine();
System.out.println("他：" + line);
socket.shutdownInput();
socket.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
