1. Ethereum is an open source public blockchain platform with smart contract function. It provides decentralized virtual machine (Ethereum virtual machine) to process point-to-point contract through its special cryptocurrency ether (also known as "Ethereum")
The token on the
blockchain is called ether, and the code is eth. It can be traded in many foreign exchange markets of cryptocurrency, and it is also the medium used to pay transaction fees and computing services on Ethereum
the concept of Ethereum was first proposed by vitalik buterin, a programmer, from 2013 to 2014, inspired by bitcoin, with the general meaning of "next generation cryptocurrency and decentralized application platform", and began to develop through ICO crowdfunding in 2014. As of February 2018, Ethernet is the second highest cryptocurrency in market value, second only to bitcoin
extended data:
Ethereum platform has no characteristics and value. Like programming languages, it's up to entrepreneurs and developers to decide what to use. However, it is clear that some application types benefit more from the functions of Ethereum than others. Ethereum is especially suitable for those applications that automatically interact directly between points or promote group coordination activities across networks
for example, coordinate the application of point-to-point market, or the automation of complex financial contracts. Bitcoin enables indivials to exchange money without the help of financial institutions, banks or governments. The impact of Ethereum may be more profound
in theory, any complex financial activities or transactions can be automatically and reliably carried out on Ethereum with coding. In addition to financial applications, any application scenario with high requirements for trust, security and persistence, such as asset registration, voting, management and Internet of things, will be affected by Ethereum platform on a large scale
2. Ethereum one click coin, the specific technical content is not very clear, but this operation is safe? Does digital financial security allow the operation of one key currency issuing?
3. curl方法，file_get_contents,
4. If you want to query the transaction records on the main network, you can use Etherscan. However, if you build your own private chain, how should you query the transaction records
the answer is that you need to listen to the logs on the chain, save them in the database, and then query them in the database. For example:
< pre t = "code" L = "Java" > varaddr = & quot& quot;< br />varfilter=web3.eth.filter({fromB lock:0 ,toBlock:' latest', address:addr });< br />filter.get(function(err,transactions){
transactions.forEach(function(tx){
vartxInfo=web3.eth.getTransaction(tx.transactionHash);
/ / at this time, the transaction information txinfo can be stored in the database
})< br />});
Web3. Eth. Filter() is used to monitor the log on the chain, and Web3. Eth. Gettransaction() is used to extract the information of the specified transaction. Once the transaction information is obtained, it can be stored in the database for query
recommend a practical introction, you can see: Ethereum tutorial
5. Through curl to simulate, and then get the data, and use it in JSON format
6. Where are you going? Wallet or exchange
transfer eth, as long as there is an address, you can transfer it out
mnemonic words are things that you can help to find when you forget your key, not related to money collection.
7. Ethereum specifies the JSON RPC API application development interface that each node needs to implement. This interface is transport independent. Applications can use this interface protocol to operate Ethereum nodes through HTTP, websocket or IPC and other communication mechanisms:
8. 1. In the field of control, the system is often composed of decentralized subsystems; And each subsystem often uses the equipment and solutions of different manufacturers. Users need to integrate these subsystems and build a unified real-time monitoring system. 2. Such a real-time monitoring system needs to solve the data sharing among distributed subsystems, and each subsystem needs to coordinate the corresponding control instructions. 3. Considering that the real-time monitoring system often needs to be upgraded and adjusted. 4. All subsystems need to have a unified open interface. 5. OPC (OLE for process control) specification is the proct of this thinking. 6. OPC is based on Microsoft's distributed Internet application (DNA) architecture and component object model (COM) technology, and is designed for easy extensibility. OPC specification defines an instry standard interface. 7. OPC is a communication standard based on OLE / COM mechanism. Ole / COM is a client / server mode, which has the advantages of language independence, code reuse and easy integration. OPC standardizes the interface function, no matter what form the field device exists, the customer will visit it in a unified way, so as to ensure the transparency of the software to the customer, and make the user completely separated from the low-level development. 8. OPC defines an open interface on which PC based software components can exchange data. It is based on OLE object linking and embedding, COM component object model and DCOM Distributed COM. Therefore, OPC provides an ideal way for typical field devices in automation layer to connect instrial applications and office programs. OPC application domain 1, instrial control solution user 2, building control solution user 3, instrial control solution manufacturer 4, building control solution manufacturer 5, instrial control solution integrator 6, building control solution integrator 7, all automation fields OPC is a software interface standard for connecting data source (OPC server) and data user (OPC application program). The data source can be PLC, DCS, bar code reader and other control equipment. According to the composition of control system, OPC server as data source can be local OPC server running on the same computer with OPC application program, or remote OPC server running on another computer. OPC interface can not only be used to provide the original data of the lowest level control equipment to HMI (hardware supervision interface) / SCADA (supervision control and data acquisition), batch processing and other automation programs as data users (OPC application program) through the network, but also can be used to directly connect the application program and physical equipment. So OPC interface is an interface standard with high thickness and flexibility, which is suitable for many systems. What does OPC solve? Before the birth of OPC, there was no unified standard for the interface between the hardware driver and its connected application. For example, in the field of FA (factory automation) - factory automation, connecting PLC (programmable logic controller) and other control equipment with SCADA / HMI Software requires different FA network systems. According to a survey, in the cost of control system software development, the application program design of various machines accounts for 70% of the cost, while the development of the connection interface between machines and equipment accounts for 30%. In addition, in the PA (process automation) - process automation field, when you want to transfer all the process data in the distributed control system (DCS) to the proction management system, you must develop a specific interface according to each model of each supplier, for example, Use C language DLL (dynamic link database) to connect DDE (dynamic data exchange) server or use FTP (File Transfer Protocol) text to design application program. For example, when the system is composed of four kinds of control devices and their connected monitoring, trend diagram and reporting applications, it must spend a lot of time to develop the interface software of monitoring, trend diagram and reporting applications corresponding to devices a, B, C and D respectively. A total of 12 kinds of drivers are used. At the same time, e to the coexistence of various drives in the system, it is more difficult to maintain the stability and reliability of the operating environment. OPC is proposed for the purpose of standardizing the software interface between the devices and applications of different suppliers and simplifying the data exchange between them. As a result, it can provide users with process control software component procts that can be freely combined and used without depending on specific development language and development environment. The system using OPC is composed of OPC server which provides data collection service according to the requirements of application program (client program), OPC interface which is necessary for using OPC server, and OPC application program which receives service. OPC server is developed according to the hardware of each supplier, so that it can absorb the differences of hardware and system of each supplier, so as to realize the system composition independent of hardware. At the same time, by using a data type called variant, the data format can be provided according to the requirements of the application program, independent of the inherent data type in the hardware. Using OPC to standardize the interface can form a system as shown in Figure 5. As can be seen from Figure 5, users can choose monitoring, trend chart and reporting applications independent of the internal structure of devices a, B, C and D and their suppliers. Why develop independent OPC server and OPC gateway? 1. The high price of foreign original manufacturers; 2. The inflexibility of foreign original manufacturers in the face of projects; 3. The diversity of subsystem in domestic projects is difficult to provide driver; 4. The pursuit of independent OPC server is stable, real-time and fast. 5. Nonstandard of many subsystems 6. Possible inconsistency of EPC project before and after bidding 7. Expensive original platform server software 8. Whether the general contractor has invested a lot of manpower in the integration 9. Compatibility of platform and subsystem 10. Establishment of interoperability between OPC platform and subsystem 11. Solving the troubles of manufacturers and integrators in project integration 12 To solve the problem of distributed resources for secondary development by manufacturers and integrators 13. To solve the problem of subsystem manufacturers 14. To provide a transparent channel for data communication between upper and lower levels kayak, 2009-07-31 12:53:18 OPC interface, wrote a lot.
