Java NIO实现websocket聊天室实例
WebSocket协议
WebSocket是一种在单个TCP连接上进行全双工通信的协议。 WebSocket使得客户端和服务器之间的数据交换变得更加简单，允许服务端主动向客户端推送数据。在WebSocket API中，浏览器和服务器只需要完成一次握手，两者之间就直接可以创建持久性的连接，并进行双向数据传输。
WebSocket协议相比于Http协议来说，最大的特点就是可以实现服务端主动向客户端发送消息。在WebSocket出现之前，如果客户端想实时获取服务端的消息，就需要使用AJAX轮询，查询是否有消息，这样就很消耗服务器资源和带宽。但是用WebSocket就可以实现服务端主动向客户端发送数据，并且只需要占用一个TCP连接，节省了资源和带宽。
Java NIO 实现 websocket聊天室
接下来我们将利用Java NIO 来实现一个websocket实例，部分代码如下。
NIO的常规代码：
selector.select(1000);
Set<SelectionKey> selectionKeys = selector.selectedKeys();
Iterator<SelectionKey> it = selectionKeys.iterator();
while (it.hasNext()) {
SelectionKey key = it.next();
it.remove();
if (key.isAcceptable()) {
handleAccept(key);
}
if (key.isReadable()) {
handleRead(key);
}
}接受连接：
public void handleAccept(SelectionKey key) {
ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
SocketChannel sc;
try {
sc = ssc.accept();
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
System.out.println(String.format("[server] -- client %s connected.", sc.getRemoteAddress().toString()));
} catch (IOException e) {
System.out.println(String.format("[server] -- error occur when accept: %s.", e.getMessage()));
key.cancel();
}
}
读取通道中的数据：
public void handleRead(SelectionKey key) {
SocketChannel sc = (SocketChannel) key.channel();
Client client = (Client) key.attachment();
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
// 如果是第一次连接进来，就需要创建一个客户端对象，存储起来
if (client == null) {
client = new Client(sc);
clients.add(client);
key.attach(client);
byteBuffer.clear();
// 如果连接还没有建立，就是要HTTP建立连接
try {
sc.read(byteBuffer);
byteBuffer.flip();
String response = WebSocketHandler.getResponse(new String(byteBuffer.array()));
byteBuffer.clear();
byteBuffer.put(response.getBytes());
byteBuffer.flip();
while (byteBuffer.hasRemaining()) {
sc.write(byteBuffer);
}
} catch (IOException e) {
System.out.println(String.format("[server] -- error occur when read: %s.", e.getMessage()));
}
String message = "[系统消息] " + client.toString() + " 加入了群聊";
broadcast(message.getBytes(), client);
}
byteBuffer.clear();
int read = 0;
try {
read = sc.read(byteBuffer);
if (read > 0) {
byteBuffer.flip();
int opcode = byteBuffer.get() & 0x0f;
// 8表示客户端关闭了连接
if (opcode == 8) {
System.out.println(String.format("[server] -- client %s connection close.", sc.getRemoteAddress()));
clients.remove(client);
String message = "[系统消息] " + client.toString() + " 退出了群聊";
broadcast(message.getBytes(), client);
sc.close();
key.cancel();
return;
}
// 只考虑了最简单的payload长度情况。
int len = byteBuffer.get();
len &= 0x7f;
byte[] mask = new byte[4];
byteBuffer.get(mask);
byte[] payload = new byte[len];
byteBuffer.get(payload);
for (int i = 0; i < payload.length; i++) {
payload[i] ^= mask[i % 4];
}
System.out.println(String
.format("[server] -- client: [%s], send: [%s].", client.toString(), new String(payload)));
String message = String.format("[%s]: %s", client.toString(), new String(payload));
broadcast(message.getBytes(), client);
} else if (read == -1) {
System.out.println(String.format("[server] -- client %s connection close.", sc.getRemoteAddress()));
clients.remove(client);
String message = "[系统消息] " + client.toString() + " 退出了群聊";
broadcast(message.getBytes(), client);
sc.close();
key.cancel();
}
} catch (IOException e) {
System.out.println(String.format("[server] -- error occur when read: %s.", e.getMessage()));
}
}使用HTTP建立WebSocket连接。
public class WebSocketHandler {
private static String APPEND_STRING = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
static class Header {
private Map<String, String> properties = new HashMap<>();
public String get(String key) {
return properties.get(key);
}
}
private WebSocketHandler() {}
private static Header phrase(String request) {
Header header = new Header();
String[] pros = request.split("\r\n");
for (String pro : pros) {
if (pro.contains(":")) {
int index = pro.indexOf(":");
String key = pro.substring(0, index).trim();
String value = pro.substring(index + 1).trim();
header.properties.put(key, value);
}
}
return header;
}
public static String getResponse(String request) {
Header header = phrase(request);
String acceptKey = header.get("Sec-WebSocket-Key") + APPEND_STRING;
MessageDigest sha1;
try {
sha1 = MessageDigest.getInstance("sha1");
sha1.update(acceptKey.getBytes());
acceptKey = new String(Base64.getEncoder().encode(sha1.digest()));
} catch (NoSuchAlgorithmException e) {
System.out.println("fail to encode " + e.getMessage());
return null;
}
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("HTTP/1.1 101 Switching Protocols\r\n").append("Upgrade: websocket\r\n")
.append("Connection: Upgrade\r\n").append("Sec-WebSocket-Accept: " + acceptKey + "\r\n")
.append("\r\n");
return stringBuilder.toString();
}
}客户端对象
/**
* @author XinHui Chen
* @date 2020/2/8 19:20
*/
public class Client {
private SocketChannel socketChannel = null;
private String id = null;
public SocketChannel getSocketChannel() {
return socketChannel;
}
public String getId() {
return id;
}
Client(SocketChannel socketChannel) {
this.socketChannel = socketChannel;
this.id = UUID.randomUUID().toString();
}
@Override
public String toString() {
try {
return id + " " + socketChannel.getRemoteAddress().toString();
} catch (IOException e) {
System.out.println(e.getMessage());
return null;
}
}
}结果
使用网页和控制台与服务端建立WebSocket连接，发送数据。两个都能成功显示。
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版权声明：本文为CSDN博主「p0150n0us」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/aaacccadobe/article/details/104249333