Socket 实例（服务器端）

Socket是与客户端交互的基础类。它继承了 Node.jsEventEmitter的所有方法，例如emit, on, once 或 removeListener.

除了：

• 发出 和 监听 事件
• 广播事件
• 加入和离开房间

Socket 实例有一些可能在您的应用程序中使用的属性：

Socket#id

每个新连接都分配有一个随机的 20 个字符的标识符。

此标识符与客户端的值同步。

// server-side
io.on("connection", (socket) => {
  console.log(socket.id); // ojIckSD2jqNzOqIrAGzL
});

// client-side
socket.on("connect", () => {
  console.log(socket.id); // ojIckSD2jqNzOqIrAGzL
});

创建后，Socket 会加入由其自己的 id 标识的房间，这意味着您可以将其用于私人消息传递：

io.on("connection", socket => {
  socket.on("private message", (anotherSocketId, msg) => {
    socket.to(anotherSocketId).emit("private message", socket.id, msg);
  });
});

注意：您不能覆盖此标识符，因为它在 Socket.IO 代码库的多个部分中使用。

Socket#handshake

此对象包含有关在 Socket.IO 会话开始时发生的握手的一些详细信息。

{
  headers: /* the headers of the initial request */
  query: /* the query params of the initial request */
  auth: /* the authentication payload */
  time: /* the date of creation (as string) */
  issued: /* the date of creation (unix timestamp) */
  url: /* the request URL string */
  address: /* the ip of the client */
  xdomain: /* whether the connection is cross-domain */
  secure: /* whether the connection is secure */
}

例子：

{
  "headers": {
    "user-agent": "xxxx",
    "accept": "*/*",
    "host": "example.com",
    "connection": "close"
  },
  "query": {
    "EIO": "4",
    "transport": "polling",
    "t": "NNjNltH"
  },
  "auth": {
    "token": "123"
  },
  "time": "Sun Nov 22 2020 01:33:46 GMT+0100 (Central European Standard Time)",
  "issued": 1606005226969,
  "url": "/socket.io/?EIO=4&transport=polling&t=NNjNltH",
  "address": "::ffff:1.2.3.4",
  "xdomain": false,
  "secure": true
}

Socket#rooms

这是对 Socket 当前所在房间的引用。

io.on("connection", (socket) => {
  console.log(socket.rooms); // Set { <socket.id> }
  socket.join("room1");
  console.log(socket.rooms); // Set { <socket.id>, "room1" }
});

Socket#data

可以与fetchSockets()实用程序方法结合使用的任意对象：

// server A
io.on("connection", (socket) => {
  socket.data.username = "alice";
});

// server B
const sockets = await io.fetchSockets();
console.log(sockets[0].data.username); // "alice"

更多信息在这里.

Socket#conn

对底层 Engine.IO 套接字的引用（参见此处）。

io.on("connection", (socket) => {
  console.log("initial transport", socket.conn.transport.name); // prints "polling"

  socket.conn.once("upgrade", () => {
    // called when the transport is upgraded (i.e. from HTTP long-polling to WebSocket)
    console.log("upgraded transport", socket.conn.transport.name); // prints "websocket"
  });

  socket.conn.on("packet", ({ type, data }) => {
    // called for each packet received
  });

  socket.conn.on("packetCreate", ({ type, data }) => {
    // called for each packet sent
  });

  socket.conn.on("drain", () => {
    // called when the write buffer is drained
  });

  socket.conn.on("close", (reason) => {
    // called when the underlying connection is closed
  });
});

Additional attributes

只要您不覆盖任何现有属性，您就可以将任何属性附加到 Socket 实例并在以后使用它：

// in a middleware
io.use(async (socket, next) => {
  try {
    const user = await fetchUser(socket);
    socket.user = user;
  } catch (e) {
    next(new Error("unknown user"));
  }
});

io.on("connection", (socket) => {
  console.log(socket.user);

  // in a listener
  socket.on("set username", (username) => {
    socket.username = username;
  });
});

Socket middlewares

这些中间件看起来很像通常的中间件，除了它们是为每个传入的数据包调用的：

socket.use(([event, ...args], next) => {
  // do something with the packet (logging, authorization, rate limiting...)
  // do not forget to call next() at the end
  next();
});

next也可以使用错误对象调用该方法。在这种情况下，事件将不会到达注册的事件处理程序，而error是会发出一个事件：

io.on("connection", (socket) => {
  socket.use(([event, ...args], next) => {
    if (isUnauthorized(event)) {
      return next(new Error("unauthorized event"));
    }
    next();
  });

  socket.on("error", (err) => {
    if (err && err.message === "unauthorized event") {
      socket.disconnect();
    }
  });
});

注意：此功能仅存在于服务器端。对于客户端，您可能对catch-all listeners感兴趣。

Events

在服务器端，Socket 实例发出两个特殊事件：

• disconnect
• disconnecting

disconnect

此事件由 Socket 实例在断开连接时触发。

io.on("connection", (socket) => {
  socket.on("disconnect", (reason) => {
    // ...
  });
});

以下是可能的原因列表：

Reason	Description
server namespace disconnect	socket被socket.disconnect强行断开
client namespace disconnect	客户端使用socket.disconnect()手动断开socket
server shutting down	服务器正在关闭
ping timeout	pingTimeout 客户端在延迟中没有发送 PONG 数据包
transport close	连接已关闭（例如：用户失去连接，或网络从 WiFi 更改为 4G）
transport error	连接遇到错误

disconnecting

当Socket#rooms集不为空时，此事件类似于disconnect但更早触发。

io.on("connection", (socket) => {
  socket.on("disconnecting", (reason) => {
    for (const room of socket.rooms) {
      if (room !== socket.id) {
        socket.to(room).emit("user has left", socket.id);
      }
    }
  });
});

注意：这些事件以及connect, connect_error, newListener 和 removeListener是不应在您的应用程序中使用的特殊事件:

// BAD, will throw an error
socket.emit("disconnect");

完整API

可以在此处找到 Socket 实例公开的完整 API 。