Server-side data encrypted with aes, repass base64 encoding, and then spread to the client

After the client receives, first solve base64, reduction for aes buffer, then revert to the original

The question now is: due to each end of the buffer size is not consistent, may the client receives the base64 is not complete, or a few base64 data merged together
So from the incomplete or multiple base64 data, reduction of aes data, it is possible and the original distinguishing

My question is: how to avoid the problem of network transmission aes data exception