serial modem driver problem

[Harsha111]

Problem
----------
I have written serial driver for modem by polling mechanism.
PPP protocol able to call my serial driver API's
but when I try to access internet via modem it throws
carrier Lost error

Test behaviour in-sequence
---------------------------
send ATD dial number to modem
receives CONNECT response from modem
send/receive junk from/to modem for some time
send user ID & Password to modem
send/receive junk from/to modem for some time
then only PPP calls serial read mthod and it is not sending
the URL to modem
after long time modem throws Carrier Lost error

Would you please tell me what will be the reason for this behaviour?

Thanks in advance

[Pype.Clicker]

saying that you're "sending the URL to the modem" seems strange to me. I'm not sure, but most of the time, there's a protocol to be implemented atop of PPP (is it SLIP ?)

And certainly you should use the IP protocol atop of that before you send TCP connections and URLs ...

[harsha1112]

>there's a protocol to be implemented atop of PPP (is >it .SLIP ?)

Yes. I have protocol stack like TCP/IP-->PPP-->Serial modem driver.

I think there is problem only in my serial modem driver.bcoz i have already tested with TCP/IP --> PPP-->win32 serial driver and it is working fine.

Setting done for my serial modem driver

Baud rate: 115200
flags : no parity | 8 data bits | one stop bit
Flow control : None

Everytime when I try to test my serial driver via browser
exactly in same stage it stucks


Test behaviour in-sequence
---------------------------
send ATD dial number to modem
receives CONNECT response from modem
send/receive junk from/to modem for some time
send user ID & Password to modem
send/receive junk from/to modem for some time

after long time modem throws DCD de-asserted "Carrier Lost error"

Plz help me out to solve this problem.

[Pype.Clicker]

yes, i've read your test sequence already, but what troubles me there is the "send/recv junk" ... junk like in "values really don't care"? just sounds weird to me.

I'm not really a modem guru, but anywhere else in computer networks, having a connection closed (here the 'carrier lost') usually has two possible meanings:
1. you sent something your peer didn't like. He assumed your state is inconsistent and closes the connection
2. you failed to do something in the allowed amount of time. If some ACK is required before the connection is definitely established and if you didn't send the ACK, the connection will eventually be closed if left half open.

[harsha1112]

Thanks for your reply.

Tested these two problem by comparing my serial driver
& win32 serial driver using debug tool
send & receive methods input parameters & output parameters(data & size) are same in both the cases upto before getting the error.

....After sending loginID & password
data sending "CZ..0!AA" size = 30
receives some response
data sending "CZ..0!OA" size = 18
receives some response
data sending "CZ..0!AB" size = 30
receives some response
data sending "CZ..0!BB" size = 18
receives some response

*After this state in my serial driver
only receives response contineously from modem

*After this state in win32 serial driver
sending URL to modem with size 64

May be I have struck with the option-2.

Do you have any idea about the ACK expected before the connection is definitely established ?