net: fix non-blocking read/write (#20438)

vlib/net/socket.v

@@ -9,3 +9,20 @@ pub:
 pub fn (s &Socket) address() !Addr {
 	return addr_from_socket_handle(s.handle)
 }
+
+// set_blocking will change the state of the socket to either blocking,
+// when state is true, or non blocking (false).
+pub fn set_blocking(handle int, state bool) ! {
+	$if windows {
+		t := if state { u32(0) } else { u32(1) }
+		socket_error(C.ioctlsocket(handle, fionbio, &t))!
+	} $else {
+		mut flags := C.fcntl(handle, C.F_GETFL, 0)
+		if state {
+			flags &= ~C.O_NONBLOCK
+		} else {
+			flags |= C.O_NONBLOCK
+		}
+		socket_error(C.fcntl(handle, C.F_SETFL, flags))!
+	}
+}