socket.bind(options[, callback])

• options <Object> 必要的。包含以下属性：
  • port <integer>
  • address <string>
  • exclusive <boolean>
  • fd <integer>
• callback <Function>

对于 UDP socket，该方法会令 dgram.Socket 在指定的 port 和可选的 address 上监听数据包信息。 若 port 未指定或为 0，操作系统会尝试绑定一个随机的端口。 若 address 未指定，操作系统会尝试在所有地址上监听。 绑定完成时会触发一个 'listening' 事件，并会调用 callback 方法。

options 对象可能包含 fd 属性。 当设置大于 0 的 fd 时，它将会使用给定的文件描述符封装一个现有的 socket。 在这种情况下， port 和 address 的属性将会忽略。

同时监听 'listening' 事件和在 socket.bind() 方法中传入 callback 参数并不会带来坏处，但也不是很有用。

在配合 cluster 模块使用 dgram.Socket 对象时， options 对象可能包含一个附加的 exclusive 属性。 当 exclusive 被设为 false（默认值）时，集群工作进程会使用相同的 socket 句柄来共享连接处理作业。 当 exclusive 被设为 true 时，该句柄将不会被共享，而尝试共享端口则会造成错误。

一个绑定的数据报 socket 会使 Node.js 进程持续运行以接受数据报消息。

如果绑定失败，一个 'error' 事件会产生。在极少数情况下（例如尝试绑定一个已经关闭的 socket），一个 Error 可能抛出。

一个不共享端口的 socket 的例子如下文所示。

socket.bind({
  address: 'localhost',
  port: 8000,
  exclusive: true
});

• options <Object> Required. Supports the following properties:
  • port <integer>
  • address <string>
  • exclusive <boolean>
  • fd <integer>
• callback <Function>

For UDP sockets, causes the dgram.Socket to listen for datagram messages on a named port and optional address that are passed as properties of an options object passed as the first argument. If port is not specified or is 0, the operating system will attempt to bind to a random port. If address is not specified, the operating system will attempt to listen on all addresses. Once binding is complete, a 'listening' event is emitted and the optional callback function is called.

The options object may contain a fd property. When a fd greater than 0 is set, it will wrap around an existing socket with the given file descriptor. In this case, the properties of port and address will be ignored.

Specifying both a 'listening' event listener and passing a callback to the socket.bind() method is not harmful but not very useful.

The options object may contain an additional exclusive property that is used when using dgram.Socket objects with the cluster module. When exclusive is set to false (the default), cluster workers will use the same underlying socket handle allowing connection handling duties to be shared. When exclusive is true, however, the handle is not shared and attempted port sharing results in an error.

A bound datagram socket keeps the Node.js process running to receive datagram messages.

If binding fails, an 'error' event is generated. In rare case (e.g. attempting to bind with a closed socket), an Error may be thrown.

An example socket listening on an exclusive port is shown below.

socket.bind({
  address: 'localhost',
  port: 8000,
  exclusive: true
});