SHA1,MD5 calculation in case of where it left off

[Prabu RM]

Hi,

We have been used to CRC via MD5 hash algorithm for a file to be
transferred in socket we kepp below steps.

*At Client side:*

1.Md5 Init()
2.MD5 Update
   MD5 Update
   MD5 Update
   MD5 Update
   .
   .
   .
3.MD5 Final

4.Get Checksum *C1*

*At Server side:*

1.Md5 Init()
2.MD5 Update
   MD5 Update
   MD5 Update
   MD5 Update
   .
   .
   .
3.MD5 Final
4.Get Checksum *C2*

*if(C1 == C2)
{
    crc is sucess!
}
*
What my case is if i transfer a file with large size about 1GB and if the
socket closed at the time of file reaching 500MB and i re-transfer the file
in next schedule. In this how can i work with MD5,SHA hash algorithms where
i wish "Where it left off"?

Could you please help me? Simply how can i handle CRC of incomplete file in
next schedule? Is there any other way rather than transferring entire file?

Regards,
Prabu RM.