WebSocket

Agent 支持 WebSocket 连接以实现实时双向通信。本页介绍服务端 WebSocket 处理。客户端连接请参阅客户端 SDK。

生命周期钩子

Agent 在多个时点触发以下生命周期钩子：

Hook	调用时机
`onStart(props?)`	Agent 首次启动时（任何连接之前）一次
`onRequest(request)`	收到 HTTP 请求时（非 WebSocket）
`onConnect(connection, ctx)`	建立新 WebSocket 连接时
`onMessage(connection, message)`	收到 WebSocket 消息时
`onClose(connection, code, reason, wasClean)`	WebSocket 连接关闭时
`onError(connection, error)`	连接上发生 WebSocket 错误时
`onError(error)`	发生服务端级错误时（与特定连接无关）
`shouldSendProtocolMessages(connection, ctx)`	是否向此连接发送协议消息（identity、state、MCP）。默认：`true`

`onStart`

onStart() 在 Agent 首次启动时调用一次，早于任何连接建立：

export class MyAgent extends Agent {
	async onStart() {
		// Initialize resources
		console.log(`Agent ${this.name} starting...`);

		// Load data from storage
		const savedData = this.sql`SELECT * FROM cache`;
		for (const row of savedData) {
			// Rebuild in-memory state from persistent storage
		}
	}

	onConnect(connection) {
		// By the time connections arrive, onStart has completed
	}
}

export class MyAgent extends Agent {
	async onStart() {
		// Initialize resources
		console.log(`Agent ${this.name} starting...`);

		// Load data from storage
		const savedData = this.sql`SELECT * FROM cache`;
		for (const row of savedData) {
			// Rebuild in-memory state from persistent storage
		}
	}

	onConnect(connection: Connection) {
		// By the time connections arrive, onStart has completed
	}
}

处理连接

在 Agent 上定义 onConnect 与 onMessage 方法以接受 WebSocket 连接：

import { Agent, Connection, ConnectionContext, WSMessage } from "agents";

export class ChatAgent extends Agent {
	async onConnect(connection, ctx) {
		// Connections are automatically accepted
		// Access the original request for auth, headers, cookies
		const url = new URL(ctx.request.url);
		const token = url.searchParams.get("token");

		if (!token) {
			connection.close(4001, "Unauthorized");
			return;
		}

		// Store user info on this connection
		connection.setState({ authenticated: true });
	}

	async onMessage(connection, message) {
		if (typeof message === "string") {
			// Handle text message
			const data = JSON.parse(message);
			connection.send(JSON.stringify({ received: data }));
		}
	}
}

import { Agent, Connection, ConnectionContext, WSMessage } from "agents";

export class ChatAgent extends Agent {
	async onConnect(connection: Connection, ctx: ConnectionContext) {
		// Connections are automatically accepted
		// Access the original request for auth, headers, cookies
		const url = new URL(ctx.request.url);
		const token = url.searchParams.get("token");

		if (!token) {
			connection.close(4001, "Unauthorized");
			return;
		}

		// Store user info on this connection
		connection.setState({ authenticated: true });
	}

	async onMessage(connection: Connection, message: WSMessage) {
		if (typeof message === "string") {
			// Handle text message
			const data = JSON.parse(message);
			connection.send(JSON.stringify({ received: data }));
		}
	}
}

Connection 对象

每个已连接客户端拥有唯一的 Connection 对象：

属性/方法	类型	描述
`id`	`string`	此连接的唯一标识符
`uri`	`string \| null`	原始 WebSocket 升级请求的 URL。休眠后仍保留
`state`	`State`	每连接 state 对象
`setState(state)`	`void`	更新连接 state
`send(message)`	`void`	向此客户端发送消息
`close(code?, reason?)`	`void`	关闭连接
`tags`	`readonly string[]`	通过 `getConnectionTags` 分配的标签。始终以连接 ID 为第一项
`server`	`string`	Agent 实例名（与 Agent 上 `this.name` 相同）

每连接 state

存储各连接特有数据（用户信息、偏好等）：

export class ChatAgent extends Agent {
	async onConnect(connection, ctx) {
		const userId = new URL(ctx.request.url).searchParams.get("userId");

		connection.setState({
			userId: userId || "anonymous",
			role: "user",
			joinedAt: Date.now(),
		});
	}

	async onMessage(connection, message) {
		// Access connection-specific state
		console.log(`Message from ${connection.state.userId}`);
	}
}

interface ConnectionState {
	userId: string;
	role: "admin" | "user";
	joinedAt: number;
}

export class ChatAgent extends Agent {
	async onConnect(
		connection: Connection<ConnectionState>,
		ctx: ConnectionContext,
	) {
		const userId = new URL(ctx.request.url).searchParams.get("userId");

		connection.setState({
			userId: userId || "anonymous",
			role: "user",
			joinedAt: Date.now(),
		});
	}

	async onMessage(connection: Connection<ConnectionState>, message: WSMessage) {
		// Access connection-specific state
		console.log(`Message from ${connection.state.userId}`);
	}
}

向所有客户端广播

使用 this.broadcast() 向所有已连接客户端发送消息：

export class ChatAgent extends Agent {
	async onMessage(connection, message) {
		// Broadcast to all connected clients
		this.broadcast(
			JSON.stringify({
				from: connection.id,
				message: message,
				timestamp: Date.now(),
			}),
		);
	}

	// Broadcast from any method
	async notifyAll(event, data) {
		this.broadcast(JSON.stringify({ event, data }));
	}
}

export class ChatAgent extends Agent {
	async onMessage(connection: Connection, message: WSMessage) {
		// Broadcast to all connected clients
		this.broadcast(
			JSON.stringify({
				from: connection.id,
				message: message,
				timestamp: Date.now(),
			}),
		);
	}

	// Broadcast from any method
	async notifyAll(event: string, data: unknown) {
		this.broadcast(JSON.stringify({ event, data }));
	}
}

排除连接

传入要从广播中排除的连接 ID 数组：

// Broadcast to everyone except the sender
this.broadcast(
	JSON.stringify({ type: "user-typing", userId: "123" }),
	[connection.id], // Do not send to the originator
);

// Broadcast to everyone except the sender
this.broadcast(
	JSON.stringify({ type: "user-typing", userId: "123" }),
	[connection.id], // Do not send to the originator
);

连接标签

为连接打标签以便过滤。覆盖 getConnectionTags() 在连接建立时分配标签：

export class ChatAgent extends Agent {
	getConnectionTags(connection, ctx) {
		const url = new URL(ctx.request.url);
		const role = url.searchParams.get("role");

		const tags = [];
		if (role === "admin") tags.push("admin");
		if (role === "moderator") tags.push("moderator");

		return tags; // Up to 9 tags, max 256 chars each
	}

	// Later, broadcast only to admins
	notifyAdmins(message) {
		for (const conn of this.getConnections("admin")) {
			conn.send(message);
		}
	}
}

export class ChatAgent extends Agent {
	getConnectionTags(connection: Connection, ctx: ConnectionContext): string[] {
		const url = new URL(ctx.request.url);
		const role = url.searchParams.get("role");

		const tags: string[] = [];
		if (role === "admin") tags.push("admin");
		if (role === "moderator") tags.push("moderator");

		return tags; // Up to 9 tags, max 256 chars each
	}

	// Later, broadcast only to admins
	notifyAdmins(message: string) {
		for (const conn of this.getConnections("admin")) {
			conn.send(message);
		}
	}
}

连接管理方法

方法	Signature	描述
`getConnections`	`(tag?: string) => Iterable<Connection>`	获取所有连接，可按标签过滤
`getConnection`	`(id: string) => Connection \| undefined`	按 ID 获取连接
`getConnectionTags`	`(connection, ctx) => string[]`	覆盖以给连接打标签
`broadcast`	`(message, without?: string[]) => void`	发送到所有连接
`isConnectionReadonly`	`(connection) => boolean`	检查连接是否为只读
`isConnectionProtocolEnabled`	`(connection) => boolean`	检查此连接是否启用协议消息

处理二进制数据

消息可为字符串或二进制（ArrayBuffer / ArrayBufferView）：

export class FileAgent extends Agent {
	async onMessage(connection, message) {
		if (message instanceof ArrayBuffer) {
			// Handle binary upload
			const bytes = new Uint8Array(message);
			await this.processFile(bytes);
			connection.send(
				JSON.stringify({ status: "received", size: bytes.length }),
			);
		} else if (typeof message === "string") {
			// Handle text command
			const command = JSON.parse(message);
			// ...
		}
	}
}

export class FileAgent extends Agent {
	async onMessage(connection: Connection, message: WSMessage) {
		if (message instanceof ArrayBuffer) {
			// Handle binary upload
			const bytes = new Uint8Array(message);
			await this.processFile(bytes);
			connection.send(
				JSON.stringify({ status: "received", size: bytes.length }),
			);
		} else if (typeof message === "string") {
			// Handle text command
			const command = JSON.parse(message);
			// ...
		}
	}
}

错误与关闭处理

处理连接错误与断开。onError 有两个重载——一个用于 WebSocket 连接错误，一个用于服务端级错误：

export class ChatAgent extends Agent {
	// WebSocket connection error

	// Server-level error (not tied to a specific connection)

	onError(connectionOrError, error) {
		if (error) {
			console.error(`Connection ${connectionOrError.id} error:`, error);
		} else {
			console.error("Server error:", connectionOrError);
		}
	}

	async onClose(connection, code, reason, wasClean) {
		console.log(`Connection ${connection.id} closed: ${code} ${reason}`);

		this.broadcast(
			JSON.stringify({
				event: "user-left",
				userId: connection.state?.userId,
			}),
		);
	}
}

export class ChatAgent extends Agent {
	// WebSocket connection error
	onError(connection: Connection, error: unknown): void;
	// Server-level error (not tied to a specific connection)
	onError(error: unknown): void;
	onError(connectionOrError: Connection | unknown, error?: unknown) {
		if (error) {
			console.error(
				`Connection ${(connectionOrError as Connection).id} error:`,
				error,
			);
		} else {
			console.error("Server error:", connectionOrError);
		}
	}

	async onClose(
		connection: Connection,
		code: number,
		reason: string,
		wasClean: boolean,
	) {
		console.log(`Connection ${connection.id} closed: ${code} ${reason}`);

		this.broadcast(
			JSON.stringify({
				event: "user-left",
				userId: connection.state?.userId,
			}),
		);
	}
}

默认 onError 实现会记录错误并重新抛出。覆盖它以添加自定义错误处理、上报或恢复逻辑。

消息类型

类型	描述
`string`	文本消息（通常为 JSON）
`ArrayBuffer`	二进制数据
`ArrayBufferView`	二进制数据的类型化数组视图

休眠

Agent 支持休眠——不活跃时可睡眠，需要时唤醒。在保持 WebSocket 连接的同时节省资源。

启用休眠

休眠默认启用。要禁用：

export class AlwaysOnAgent extends Agent {
	static options = { hibernate: false };
}

export class AlwaysOnAgent extends Agent {
	static options = { hibernate: false };
}

休眠工作原理

Agent 活跃，处理连接
一段时间无消息不活跃后，Agent 休眠（睡眠）
WebSocket 连接保持打开（由 Cloudflare 处理）
消息到达时 Agent 唤醒
正常调用 onMessage

休眠后仍保留的内容

保留	不保留
`this.state`（Agent state）	内存变量
`connection.state`	定时器/interval
SQLite 数据（`this.sql`）	进行中的 Promise
连接元数据	本地缓存

将重要数据存入 this.state 或 SQLite，而非类属性：

export class MyAgent extends Agent {
	initialState = { counter: 0 };

	// Do not do this - lost on hibernation
	localCounter = 0;

	onMessage(connection, message) {
		// Persists across hibernation
		this.setState({ counter: this.state.counter + 1 });

		// Lost after hibernation
		this.localCounter++;
	}
}

export class MyAgent extends Agent<Env, { counter: number }> {
	initialState = { counter: 0 };

	// Do not do this - lost on hibernation
	private localCounter = 0;

	onMessage(connection: Connection, message: WSMessage) {
		// Persists across hibernation
		this.setState({ counter: this.state.counter + 1 });

		// Lost after hibernation
		this.localCounter++;
	}
}

常见模式

在线状态跟踪

使用每连接 state 跟踪在线用户。用户断开时连接 state 自动清理：

export class PresenceAgent extends Agent {
	onConnect(connection, ctx) {
		const url = new URL(ctx.request.url);
		const name = url.searchParams.get("name") || "Anonymous";

		connection.setState({
			name,
			joinedAt: Date.now(),
			lastSeen: Date.now(),
		});

		// Send current presence to new user
		connection.send(
			JSON.stringify({
				type: "presence",
				users: this.getPresence(),
			}),
		);

		// Notify others that someone joined
		this.broadcastPresence();
	}

	onClose(connection) {
		// No manual cleanup needed - connection state is automatically gone
		this.broadcastPresence();
	}

	onMessage(connection, message) {
		if (message === "ping") {
			connection.setState((prev) => ({
				...prev,
				lastSeen: Date.now(),
			}));
			connection.send("pong");
		}
	}

	getPresence() {
		const users = {};
		for (const conn of this.getConnections()) {
			if (conn.state) {
				users[conn.id] = {
					name: conn.state.name,
					lastSeen: conn.state.lastSeen,
				};
			}
		}
		return users;
	}

	broadcastPresence() {
		this.broadcast(
			JSON.stringify({
				type: "presence",
				users: this.getPresence(),
			}),
		);
	}
}

type UserState = {
	name: string;
	joinedAt: number;
	lastSeen: number;
};

export class PresenceAgent extends Agent {
	onConnect(connection: Connection<UserState>, ctx: ConnectionContext) {
		const url = new URL(ctx.request.url);
		const name = url.searchParams.get("name") || "Anonymous";

		connection.setState({
			name,
			joinedAt: Date.now(),
			lastSeen: Date.now(),
		});

		// Send current presence to new user
		connection.send(
			JSON.stringify({
				type: "presence",
				users: this.getPresence(),
			}),
		);

		// Notify others that someone joined
		this.broadcastPresence();
	}

	onClose(connection: Connection) {
		// No manual cleanup needed - connection state is automatically gone
		this.broadcastPresence();
	}

	onMessage(connection: Connection<UserState>, message: WSMessage) {
		if (message === "ping") {
			connection.setState((prev) => ({
				...prev!,
				lastSeen: Date.now(),
			}));
			connection.send("pong");
		}
	}

	private getPresence() {
		const users: Record<string, { name: string; lastSeen: number }> = {};
		for (const conn of this.getConnections<UserState>()) {
			if (conn.state) {
				users[conn.id] = {
					name: conn.state.name,
					lastSeen: conn.state.lastSeen,
				};
			}
		}
		return users;
	}

	private broadcastPresence() {
		this.broadcast(
			JSON.stringify({
				type: "presence",
				users: this.getPresence(),
			}),
		);
	}
}

带广播的聊天室

export class ChatRoom extends Agent {
	onConnect(connection, ctx) {
		const url = new URL(ctx.request.url);
		const username = url.searchParams.get("username") || "Anonymous";

		connection.setState({ username });

		// Notify others
		this.broadcast(
			JSON.stringify({
				type: "join",
				user: username,
				timestamp: Date.now(),
			}),
			[connection.id], // Do not send to the joining user
		);
	}

	onMessage(connection, message) {
		if (typeof message !== "string") return;

		const { username } = connection.state;

		this.broadcast(
			JSON.stringify({
				type: "message",
				user: username,
				text: message,
				timestamp: Date.now(),
			}),
		);
	}

	onClose(connection) {
		const { username } = connection.state || {};
		if (username) {
			this.broadcast(
				JSON.stringify({
					type: "leave",
					user: username,
					timestamp: Date.now(),
				}),
			);
		}
	}
}

type Message = {
	type: "message" | "join" | "leave";
	user: string;
	text?: string;
	timestamp: number;
};

export class ChatRoom extends Agent {
	onConnect(connection: Connection, ctx: ConnectionContext) {
		const url = new URL(ctx.request.url);
		const username = url.searchParams.get("username") || "Anonymous";

		connection.setState({ username });

		// Notify others
		this.broadcast(
			JSON.stringify({
				type: "join",
				user: username,
				timestamp: Date.now(),
			} satisfies Message),
			[connection.id], // Do not send to the joining user
		);
	}

	onMessage(connection: Connection, message: WSMessage) {
		if (typeof message !== "string") return;

		const { username } = connection.state as { username: string };

		this.broadcast(
			JSON.stringify({
				type: "message",
				user: username,
				text: message,
				timestamp: Date.now(),
			} satisfies Message),
		);
	}

	onClose(connection: Connection) {
		const { username } = (connection.state as { username: string }) || {};
		if (username) {
			this.broadcast(
				JSON.stringify({
					type: "leave",
					user: username,
					timestamp: Date.now(),
				} satisfies Message),
			);
		}
	}
}

抑制协议消息

默认 Agent 向每个连接发送 JSON 文本帧（identity、state 同步、MCP server 列表）。覆盖 shouldSendProtocolMessages 可为特定连接抑制——例如无法处理 JSON 文本帧的纯二进制客户端：

export class IoTAgent extends Agent {
	shouldSendProtocolMessages(connection, ctx) {
		const url = new URL(ctx.request.url);
		return url.searchParams.get("protocol") !== "binary";
	}
}

export class IoTAgent extends Agent {
	shouldSendProtocolMessages(
		connection: Connection,
		ctx: ConnectionContext,
	): boolean {
		const url = new URL(ctx.request.url);
		return url.searchParams.get("protocol") !== "binary";
	}
}

返回 false 时，连接不会收到身份、状态或 MCP 服务器列表帧——连接时与广播均不会。连接仍可收发常规消息、使用 RPC 并参与所有非协议通信。

使用 isConnectionProtocolEnabled(connection) 在运行时检查任意连接状态。

Agent 属性

任意 Agent 方法内的 this 上可用以下属性：

属性	类型	描述
`this.name`	`string`	此 Agent 的实例名
`this.state`	`State`	当前 Agent state（从 SQLite 懒加载）
`this.env`	`Env`	Worker 环境绑定
`this.ctx`	`DurableObjectState`	Durable Object 上下文（storage、alarm 等）
`this.sql`	template tag	针对 Agent SQLite 存储执行查询的 SQL 模板标签
`this.mcp`	`MCPClientManager`	连接外部 MCP server 的 MCP client 管理器

从客户端连接

浏览器连接请使用 Agents 客户端 SDK：

Vanilla JS：agents/client 的 AgentClient
React：agents/react 的 useAgent hook

完整文档请参阅客户端 SDK。

后续步骤

State 同步

在 Agent 与客户端之间同步 state。

可调用方法

通过 WebSocket 的 RPC 方法调用。

跨域身份验证

跨域安全 WebSocket 连接。