Using dbExpress Connections
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dbExpress is a set of lightweight database drivers that provide fast access to SQL database servers. dbExpress provides drivers for direct SQL database server access as well as through the DataSnap server.
When using a DataSnap server, the client does not need the SQL database server connectivity client, because DataSnap provides complete proxy functionality. Besides relational data, server methods can be invoked using this type of connection. This allows access to server side logic and user objects.
dbExpress connection uses two communication protocols: TCP/IP and HTTP. Depending on the customer security constraints, the client can choose one or the other. From the client perspective, there is no functional difference between the two types, hence the protocol can be chosen at run time.
Both protocols offer callback functionality.