Running Ubuntu Linux and attaching a serial to USB converter.
We have some hardware that “should” be polling another device for status via one of eight serial ports. We need to connect to each of the ports and see what it being sent.

We discovered that running dmesg | grep tty
Indicates that the device is port: /dev/ttyUSB0

That may be wrong but it’s the best I can do. So I start putty and it opens a dialog where we select the port, enter the baud rate, and select Open. The configuration dialog closes and a terminal window is open, blank. It displays nothing at all. We can get it to prompt to Wait or Close but nothing else.

Is there a method that can get us back to the configuration dialog or must we quit and restart putty every time?
Is there some method to determine if the port we have entered is correct?

To return to the configuration dialog for the running session select "Change Settings..." from the menu (right-click on the title bar in Windows).
The "correct" port depends on the protocol selected, although one can telnet to most any port. Are you using the telnet protocol?

Once I get to the dialog showing what is on the port, there is no way to show the settings again. The intent is not to use telnet, just run putty and see what the device in the other end sends. We are getting that.

Cable E and C are connected to boxes E and C respectively and are normally connected together. I break that connection and connect the USB adapter to cable E and see that device E is outputing what is expected. I connect the adapter to C and hope to use the keyboard to send exactly what E was sending and expect to see a response. Should I see characters on the screen as I type them in the putty window. I do not.

Possible problem, box C expects CR LF pair. Putty only sends CR. Is there a way to configure putty to change between sending CR and sending CR LF pair?

I'm sorry, but have you looked at PuTTYs Help at all? Now you're asking questions that are answered there.

you are right. I got started with a question I was not able to find there, then forgot to go back to the man pages with follow up questions.
I am working that now.
Thank you for your patience.

C may not echo characters back which is why you don't see anything. You can configure putty to echo local cha racers if desired. If you can see correct characters from e then the serial port parameters should be correct.

Using a second serial adapter would be easier then swapping cables which cause problems. Do you know the serial protocol? It may or may not respond to a LF but it should be configurable.

Responding to michaelk
The hardware guys have been reluctant but I have formally requested a set of cables. A male and female to put in the circuit and a second pair of connectors to DB-9 connectors, one to send the send line to my USB adapter and the other to send the receive line to my usb adapter. Then I can use two adapters and watch both sides of the conversation. They are to make one setup for RS232 and a second for RS-422.

I am pretty sure now that the receiving device demands CR LF while the sending only sends CR. We must go back to the vendor and get the output changed from CR only to CR LF.
Thank you for taking the time to reply.

Under the terminal in PuTTY setup there is a configuration setting for sending an implicit LF in every CR. That might fix the problem.

Yes, that fixes the problem for the laptop and putty. Not to get the guys that build the edev to modify their system to output that format.
Thank you for your time.