if you do this: screen -L printf "\x6X\x6\n" exit then look at the screenlog.0 file, does it contain your ACK ?
On Tue, Aug 18, 2020 at 11:47 PM Dro Ghazarian <dghazar...@gmail.com> wrote: > Hi David, > Thank you for your quick reply. I believe I did not explain the > problem correctly. I do not want to see the actual ACK character on the > screen but rather being able to get the packet information that contains > the ACK character. To demonstrate the issue, it can be done as the > following. > > 1. from my windows machine I use putty to ssh to a linux machine. > 2. Before connecting to the linux machine, I configure the putty to log > all the SSH packets. > 3. Once connected, I issue the following command printf "test\6\n" , I > am using this command to just demonstrate the issue, we do have our > command processor that uses ACK as an acknowledgement of a received data > 4. When I look at the incoming packet log I can see that I received the > ACK character. which is the following: 28 0d 0a 74 65 73 74 06 0d 0a > .......(..test.. > 5. From the same putty terminal I create a screen session by doing : > screen -dmS test > 6. Then I connect to the session by: screen -Rr test > 7. issue the printf command again: printf "test\6\n" > 8. When looking at the incoming packets, the ACK character is missing: 27 > 0d 0a 74 65 73 74 0d 0a .......'..test.. > 9. It appears that the screen is removing the ACK character and any other > non printable character as a matter of fact. standard characters such as > bell (\7) and etc are not removed, so if I issue printf "test\7\n" I could > hear the bell sound and the incoming packet will contain 07 chracter. > 10. I have looked at the screen settings to configure the screenrc and > also changing stty settings but I am not having any luck figuring out how > to stop the screen from eating out the ACk character. > > I would really appreciate your help > > Thank you > Dro Ghazarian > > On Fri, Aug 14, 2020 at 1:28 PM david kerns <david.t.ke...@gmail.com> > wrote: > >> ACK is a non-printable char ... if you run your app in a non screen >> window, I'd be surprised if you saw them. >> Try running your app like this: app | cat -v >> should print "^F" for every ACK ... independent of screen >> >> On Fri, Aug 14, 2020 at 12:59 PM Dro Ghazarian <dghazar...@gmail.com> >> wrote: >> >>> Hi, >>> I have been trying to use screen to run a process in detached mode. >>> Our process prints ACK characters to the screen, but unfortunately the >>> screen is somehow removing non printable characters. Other known >>> characters such as bell would come through but not ACK. Is there a setting >>> that I can change to let the screen handle ACK characters? >>> >>> Thank you >>> Dro Ghazarian >>> >>
