android - adb got two same serial numbers when connected to two smart phones

Question

I have two smart phones (ZTEV788d, system Android 2.3.6) connected to a computer (Ubuntu 11.10) at the same time, using command: adb devices I got this:

List of devices attached
P753A12D    device
P753A12D    device

The serial numbers are the same!

I wrote an application in the computer side to communicate with these two phones, for example install app and push files.

I used these commands:

adb -s P753A12D install XXX.apk
adb -s P753A12D push XXX /sdcard

Now these two phones have the same serial no (P753A12D), when I run these commands I get this error:

error:more than one device

So, my questions are:

1. Is that normal that two phones to have the same serial no?
2. Can I change the serial no? if yes, how?
3. Is there any way to run these install, push commands successfully even if the serial no are the same?

BTW, the WiFi/3G network will be turned off when I'll run the test.

Answer 1

Today I found an easy solution for this issue.

adb devices -l

You'll get list of devices with their qualifiers

List of devices attached
P753A12D device usb:26200000 transport_id:1
P753A12D device usb:24400000 transport_id:2

Then you can use qualifiers instead of serial numbers like this

adb -s usb:26200000 install xxx.apk

or with transport_id and -t

adb -t 1 install xxx.apk