socket.setKeepAlive([enable][, initialDelay])

• enable <boolean> 默认值： false
• initialDelay <number> 默认值: 0
• 返回：<net.Socket> 套接字本身。

启用/禁用保持连接功能，并可选择设置在空闲套接字上发送第一次保持连接探测之前的初始延迟。

【Enable/disable keep-alive functionality, and optionally set the initial delay before the first keepalive probe is sent on an idle socket.】

设置 initialDelay（以毫秒为单位）以设置从接收到最后一个数据包到第一次保持活动探测之间的延迟时间。将 initialDelay 设置为 0 将保持默认（或之前）设置值不变。

【Set initialDelay (in milliseconds) to set the delay between the last data packet received and the first keepalive probe. Setting 0 for initialDelay will leave the value unchanged from the default (or previous) setting.】

启用保持活动功能将设置以下套接字选项：

【Enabling the keep-alive functionality will set the following socket options:】

• SO_KEEPALIVE=1
• TCP_KEEPIDLE=initialDelay
• TCP_KEEPCNT=10
• TCP_KEEPINTVL=1