--- a/NonPositionableExternalStream.st	Wed Mar 04 17:01:08 2020 +0100
+++ b/NonPositionableExternalStream.st	Wed Mar 04 17:02:50 2020 +0100
@@ -552,11 +552,12 @@
 closeFile
     <resource: #PRIVATE>
     
-    |semasToSignal|
+    |semasToSignal fd|
 
-    handle notNil ifTrue:[
+    fd := self fileHandle.
+    fd notNil ifTrue:[
         "make sure, that no select is performed on closed file descriptors"
-        semasToSignal := Processor disableFd:self fileHandle doSignal:false.
+        semasToSignal := Processor disableFd:fd doSignal:false.
         super closeFile.
 
         "tell the waiters that they must not wait any longer"
@@ -566,6 +567,7 @@
     ].
 
     "Modified: / 07-04-2017 / 14:32:00 / cg"
+    "Modified: / 04-03-2020 / 14:52:38 / Stefan Vogel"
 ! !
 
 !NonPositionableExternalStream methodsFor:'private'!
@@ -925,10 +927,12 @@
      a read operation will not block the smalltalk process), false otherwise.
      We know, that error conditions do not block, so return true for errors."
 
+    |fd|
+
     ^ readAhead notNil
-        or:[handle isNil
+        or:[(fd := self fileHandle) isNil
         or:[mode == #writeonly
-        or:[OperatingSystem readCheck:self fileHandle]]]
+        or:[OperatingSystem readCheck:fd]]]
 
     "
      |pipe|
@@ -942,7 +946,8 @@
      pipe close
     "
 
-    "Modified: 25.9.1997 / 13:08:45 / stefan"
+    "Modified: / 25-09-1997 / 13:08:45 / stefan"
+    "Modified: / 04-03-2020 / 14:51:53 / Stefan Vogel"
 !
 
 canWriteWithoutBlocking
@@ -950,9 +955,13 @@
      (i.e. a write operation will not block the smalltalk process).
      We know, that error conditions do not block, so return true for errors."
 
-    ^ handle isNil
+    |fd|
+
+    ^ (fd := self fileHandle) isNil
         or:[mode == #readonly
-        or:[OperatingSystem writeCheck:self fileHandle]]
+        or:[OperatingSystem writeCheck:fd]]
+
+    "Modified: / 04-03-2020 / 14:51:42 / Stefan Vogel"
 ! !
 
 !NonPositionableExternalStream methodsFor:'writing'!
@@ -999,6 +1008,10 @@
 
      Lange Rede kurzer Sinn: 'self blocking:' sends 'self fileDescriptor'
                               which may set handle to nil!!"
+    "for linux we set non-blocking mode, so that the whole ST with all
+     other processes does not block, when a socket or pipe is full.
+     For windows, writes are done in an own thread, so only the 
+     active process will block. For windows, #blocking: is a non-op."
     wasBlocking := self blocking:false.
 
     handle isNil ifTrue:[
@@ -1046,6 +1059,7 @@
 
     "Modified (format): / 13-02-2020 / 14:23:44 / Stefan Reise"
     "Modified: / 03-03-2020 / 16:14:41 / Stefan Vogel"
+    "Modified (format): / 04-03-2020 / 12:41:18 / Stefan Vogel"
 !
 
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