The DTN IQFeed API has three snapshot reports you can request: 5MS (5-minute snapshots), EDS (end of day), and FDS (fundamental data). You must specify a commodity type and an exchange group, such as all NASDAQ equities or all OPRA options. You can't create a custom list of symbols. You must specify S,SET PROTOCOL 6.1 because these commands only exist in 6.1 and later.
This page in the iqfeed developers website: http://www.iqfeed.net/dev/api/docs/MarketSummaryviaTCPIP.cfm
goes into more detail about the reports. There is no additional charge to use them beyond the API subscription fee, and the subscription fee for the exchange(s) you want to run the report on.
DTN IQFeed Implementation Support Specialist