fixes #19973; switch to poll on posix (#20212)

* fixes #19973; switch to poll on posix

* it is fd

* exclude lwip

* fixes lwip

* rename select to timeoutRead

* refactor into timeoutRead/timeoutWrite

* refactor common parts

Co-authored-by: xflywind <43030857+xflywind@users.noreply.github.com>

lib/pure/net.nim

@@ -203,6 +203,30 @@ type
 when defined(nimHasStyleChecks):
   {.pop.}
 
+
+when defined(posix) and not defined(lwip):
+  from posix import TPollfd, POLLIN, POLLPRI, POLLOUT, POLLWRBAND, Tnfds
+
+  template monitorPollEvent(x: var SocketHandle, y: cint, timeout: int): int =
+    var tpollfd: TPollfd
+    tpollfd.fd = cast[cint](x)
+    tpollfd.events = y
+    posix.poll(addr(tpollfd), Tnfds(1), timeout)
+
+proc timeoutRead(fd: var SocketHandle, timeout = 500): int =
+  when defined(windows) or defined(lwip):
+    var fds = @[fd]
+    selectRead(fds, timeout)
+  else:
+    monitorPollEvent(fd, POLLIN or POLLPRI, timeout)
+
+proc timeoutWrite(fd: var SocketHandle, timeout = 500): int =
+  when defined(windows) or defined(lwip):
+    var fds = @[fd]
+    selectWrite(fds, timeout)
+  else:
+    monitorPollEvent(fd, POLLOUT or POLLWRBAND, timeout)
+
 proc socketError*(socket: Socket, err: int = -1, async = false,
                   lastError = (-1).OSErrorCode,
                   flags: set[SocketFlag] = {}) {.gcsafe.}
@@ -1308,14 +1332,6 @@ proc hasDataBuffered*(s: Socket): bool =
     if s.isSsl and not result:
       result = s.sslHasPeekChar
 
-proc select(readfd: Socket, timeout = 500): int =
-  ## Used for socket operation timeouts.
-  if readfd.hasDataBuffered:
-    return 1
-
-  var fds = @[readfd.fd]
-  result = selectRead(fds, timeout)
-
 proc isClosed(socket: Socket): bool =
   socket.fd == osInvalidSocket
 
@@ -1429,7 +1445,9 @@ proc waitFor(socket: Socket, waited: var Duration, timeout, size: int,
           return min(sslPending, size)
 
     var startTime = getMonoTime()
-    let selRet = select(socket, (timeout - waited.inMilliseconds).int)
+    let selRet = if socket.hasDataBuffered: 1
+      else:
+        timeoutRead(socket.fd, (timeout - waited.inMilliseconds).int)
     if selRet < 0: raiseOSError(osLastError())
     if selRet != 1:
       raise newException(TimeoutError, "Call to '" & funcName & "' timed out.")
@@ -2063,8 +2081,7 @@ proc connect*(socket: Socket, address: string, port = Port(0),
   socket.fd.setBlocking(false)
 
   socket.connectAsync(address, port, socket.domain)
-  var s = @[socket.fd]
+  if timeoutWrite(socket.fd, timeout) != 1:
-  if selectWrite(s, timeout) != 1:
     raise newException(TimeoutError, "Call to 'connect' timed out.")
   else:
     let res = getSockOptInt(socket.fd, SOL_SOCKET, SO_ERROR)