"Resource temporarily unavailable"

hello

i have a digi portserver ts 2 that i would like to use under a linux system.
i have installed the driver and and connected to the device properly.
for my test i was using a windows notebook that was feeding the portserver and the linux box to read the data.

my problem is the following:
if i start to read the data (cat /dev/ttyaa00) and after that feeding the ts from the windows, than everything works fine.
if i start the feeding and than start the cat, than i got problems.

here is 2 scenarios that i have to illustrate my problems.
the following commands were executed in the up-to-down order

==== ==============================================
[root@varpalota root]# cat /proc/dgrp/info
version: 1.8-1

rawreadok: 0x00000001 (1)
pollrate: 0x00000014 (20)
alt_fail_open: 0x00000000 (0)

mon_debug: 0x00000000 (0)
net_debug: 0x00000000 (0)
tty_debug: 0x00000000 (0)
comm_debug: 0x00000000 (0)
ports_debug: 0x00000000 (0)
[root@varpalota root]# cat /dev/ttyaa00
==== ========================================
C: emp ome>type 93000359_j.txt > COM1
==== ==============================================

[root@varpalota root]# ditty /dev/ttyaa00 -a; fuser /dev/ttyaa00; ditty
/dev/ttyaa00 -a
/dev/ttyaa00: Resource temporarily unavailable
/dev/ttyaa00: Resource temporarily unavailable
==== ========================================

==== ==============================================
[root@varpalota root]# ditty /dev/ttyaa00 -a
onstr \033[5i offstr \033[4i term ansi
maxcps 100 maxchar 50 bufsize 100 edelay 100
forcedcd -altpin -fastbaud (9600) -printer -rtstoggle
-rtspace -dtrpace -ctspace -dsrpace -dcdpace
DTR+ RTS+ CTS- CD- DSR- RI-
startc = 0x11 stopc = 0x13
-aixon astartc = 0x0 astopc = 0x0
speed 9600 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^; erase = ^?; kill = ^U; eof = ^D; eol = ;
eol2 = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;
lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
-iuclc -ixany -imaxbel
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke

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another case:
==== ==============================================
[root@varpalota root]# cat /dev/ttyaa00
==== ========================================
C: emp ome>type 93000359_j.txt > COM1
==== ==============================================

[root@varpalota root]# cat /dev/ttyaa00

[root@varpalota root]# ps ax |grep cut|grep -v grep; ditty /dev/ttyaa00
-a; fuser /dev/ttyaa00; ditty /dev/ttyaa00 -a
/dev/ttyaa00: another process waiting on open
/dev/ttyaa00: another process waiting on open
[root@varpalota root]#

anybody has any idea what i’m doing wrong?