Programming/Kdb/Labs/Feedhandler and kdb tick environment
Cryptocurrency
A cryptocurrency, crypto-currency, or crypto is a digital asset designed to work as a medium of exchange wherein individual coin ownership records are stored in a ledger existing in a form of a computerized database using strong cryptography to secure transaction records, to control the creation of additional coins, and to verify the transfer of coin ownership. It typically does not exist in physical form (like paper money) and is typically not issued by a central authority. Cryptocurrencies typically use decentralized control as opposed to centralized digital currency and central banking systems. When a cryptocurrency is minted or created prior to issuance or issued by a single issuer, it is generally considered centralized. When implemented with decentralized control, each cryptocurrency works through distributed ledger technology, typically a blockchain, that serves as a public financial transaction database.
Bitcoin, first released as open-source software in 2009, is the first decentralized cryptocurrency. Since the release of bitcoin, other cryptocurrencies have been created.
Cryptocurrency exchanges
A cryptocurrency exchange, or a digital currency exchange (DCE), is a business that allows customers to trade cryptocurrencies or digital currencies for other assets, such as conventional fiat money or other digital currencies. Exchanges may accept credit card payements, wire transfers or other forms of payment in exchange for digital currencies or cryptocurrencies. A cryptocurrency exchange can be a market maker that typically takes the bid-ask spreads as a transaction commission for its service or, as a matching platform, simply charging fees.
Here is a list of some major cryptocurrency exchanges:
- Binance
- Binance Delivery
- Binance Futures
- Binance US
- Bitcoin.com
- Bitfinex
- bitFlyer
- Bithumb
- BitMax
- BitMEX
- Bitstamp
- Bittrex
- Blockchain.com
- Bybit
- Coinbase
- Deribit
- EXX
- FTX
- FTX US
- Gate.io
- Gemini
- HitBTC
- Huobi
- Huobi DM
- Huobi Swap
- Kraken
- Kraken Futures
- KuCoin
- OKCoin
- OKEx
- Poloniex
- ProBit
- Upbit
Feedhandler
Many cryprocurrency exchanges support both the WebSocket and REST APIs.
WebSocket
WebSocket is a computer communications protocol, providing full-duplex communication channels over a single TCP connection. The WebSocket protocol was standardized by the IETF as RFC 6455 in 2011, and the WebSocket API in Web IDL is being standardized by the W3C.
WebSocket is distinct from HTTP. Both protocols are located at layer 7 in the OSI model and depend on TCP at layer 4. Although they are different, RFC 6455 states that WebSocket
is designed to work over HTTP ports 443 and 80 as well as to support HTTP proxies and intermdeiaries,
thus making it compatible with HTTP. To achieve compatibility, the WebSocket handshake uses the HTTP Upgrade header to change from the HTTP protocol to the WebSocket protocol.
Schematically the WebSocket connection can be represented as follows:
