tcp - 如何知道 TCP 连接在 net 包中关闭？

Question

我正在实现一个小型 TCP 服务器。我如何知道我的一位客户是否已关闭？我应该尝试读取或写入并检查 err 是否为零？

Answer 1

那个线程“Best way to reliably detect that a TCP connection is closed”，使用 net.Conn 表示 'c'(也可以在 utils/ping.go 或 locale-backend/server.go 或 many other instances 中看到):

one := make([]byte, 1)
c.SetReadDeadline(time.Now())
if _, err := c.Read(one); err == io.EOF {
  l.Printf(logger.LevelDebug, "%s detected closed LAN connection", id)
  c.Close()
  c = nil
} else {
  var zero time.Time
  c.SetReadDeadline(time.Now().Add(10 * time.Millisecond))
}

对于检测超时，建议:

if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
  ...

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2019 年更新:tuxedo25提到 in the comments :

In go 1.7+, zero byte reads return immediately and will never return an error.
You must read at least one byte.

见 commit 5bcdd63和 go issue 15735

net: don't return io.EOF from zero byte reads