diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index 6e5c414892..d61d7f7cf4 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -16,6 +16,21 @@
    The license applies to all entries newer than 2009-04-28.
 */
 
+2010-09-28 17:46 UTC+0200 Przemyslaw Czerpak (druzus/at/priv.onet.pl)
+  * harbour/include/hbcom.ch
+    + added new error constant value: HB_COM_ERR_IO
+  * harbour/src/rtl/hbcom.c
+    + added translation for some important OS error code
+      in *nix builds
+    + added translation ERROR_TIMEOUT -> HB_COM_ERR_TIMEOUT
+      in Windows build.
+      TODO: check real error codes for it and also for other
+            operations like opening the same port more then
+            once and add valid translations
+    ; TODO: add some basic trnaslation for OS2 error codes.
+      HB_COM_ERR_TIMEOUT seems to be most important for portable
+      programs.
+
 2010-09-28 09:56 UTC+0200 Przemyslaw Czerpak (druzus/at/priv.onet.pl)
   * harbour/src/rtl/hbcom.c
     ! fixed typo in MS-Windows builds
diff --git a/harbour/include/hbcom.ch b/harbour/include/hbcom.ch
index b56e95517f..d52c23e2e2 100644
--- a/harbour/include/hbcom.ch
+++ b/harbour/include/hbcom.ch
@@ -125,5 +125,6 @@
 #define HB_COM_ERR_BUSY             6
 #define HB_COM_ERR_OTHER            7
 #define HB_COM_ERR_ALREADYOPEN      8
+#define HB_COM_ERR_IO               9
 
 #endif /* HB_COM_CH_ */
diff --git a/harbour/src/rtl/hbcom.c b/harbour/src/rtl/hbcom.c
index e5a670777c..521f37a188 100644
--- a/harbour/src/rtl/hbcom.c
+++ b/harbour/src/rtl/hbcom.c
@@ -296,7 +296,24 @@ int hb_comLastNum( void )
 static void hb_comSetOsError( PHB_COM pCom, HB_BOOL fError )
 {
    pCom->oserr = fError ? HB_COM_GETERROR() : 0;
-   pCom->error = pCom->oserr ? HB_COM_ERR_OTHER : 0;
+   switch( pCom->oserr )
+   {
+      case 0:
+         pCom->error = 0;
+         break;
+      case EIO:
+         pCom->error = HB_COM_ERR_IO;
+         break;
+      case EBUSY:
+         pCom->error = HB_COM_ERR_BUSY;
+         break;
+      case EAGAIN:
+         pCom->error = HB_COM_ERR_TIMEOUT;
+         break;
+      default:
+         pCom->error = HB_COM_ERR_OTHER;
+         break;
+   }
 }
 
 #if defined( HB_OS_UNIX )
@@ -1260,7 +1277,19 @@ int hb_comOpen( int iPort )
 static void hb_comSetOsError( PHB_COM pCom, BOOL fError )
 {
    pCom->oserr = fError ? GetLastError() : 0;
-   pCom->error = pCom->oserr ? HB_COM_ERR_OTHER : 0;
+
+   switch( pCom->oserr )
+   {
+      case 0:
+         pCom->error = 0;
+         break;
+      case ERROR_TIMEOUT:
+         pCom->error = HB_COM_ERR_TIMEOUT;
+         break;
+      default:
+         pCom->error = HB_COM_ERR_OTHER;
+         break;
+   }
 }
 
 int hb_comInputCount( int iPort )
@@ -1945,7 +1974,15 @@ int hb_comOpen( int iPort )
 static void hb_comSetOsError( PHB_COM pCom, APIRET rc )
 {
    pCom->oserr = rc;
-   pCom->error = rc != NO_ERROR ? HB_COM_ERR_OTHER : 0;
+   switch( pCom->oserr )
+   {
+      case NO_ERROR:
+         pCom->error = 0;
+         break;
+      default:
+         pCom->error = HB_COM_ERR_OTHER;
+         break;
+   }
 }
 
 int hb_comInputCount( int iPort )