RPC connection Ethereum wallet command

1. You can choose to trade in the digital currency exchange. At present, the mainstream digital currency exchanges in the market are coin security, fire currency and bitnet.

2. No, it only needs the currency supported by the wallet. If the currency not supported by the wallet is transferred in, the coin will be lost. The charging address of each coin is different. Moreover, the wallet is a small platform. I feel that it is not as safe as ZB, but some personal wallets can be used with some amount

3. How to run Ethereum source code go Ethereum
install MIPS based Linux header file
$CD $prjroot / kernel
$tar - xjvf linux-2.6.38. Tar. Bz2
$CD linux-2.6.38

create an include folder under the specified path to store related header files< br />$ mkdir -p $TARGET_ Prefix / include

ensures that the Linux source code is clean
$make mrproper

generates the required header file< br />$ make ARCH=mips headers_ check
$ make ARCH=mips INSTALL_ HDR_ PATH=dest headers_ Install

all the files in dest folder to the specified include folder< br />$ cp -rv dest/include/* $TARGET_ Prefix / include

delete dest folder at last
$RM - RF dest
$LS - L $target_ PREFIX/include

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. Because blockchain technology has natural advantages in realizing smart contracts. bitcoin, Ruitai, Laite, Ethereum and other digital cryptocurrencies all use blockchain technology. Blockchain is an important concept of bitcoin. In essence, it is a decentralized database and the underlying technology of bitcoin. Blockchain is a chain of uses

6. Hello
first of all, you need to have an Ethernet wallet account number and address. Then you can display the currency in your personal assets or personal account on the trading platform. Click Ethereum to withdraw the currency and fill in the address of your wallet
Mr. Yuan Wang is engaged in the development of digital asset blockchain system. If you need to develop it, you can search "Mr. Yuan Wang" on the Internet for detailed communication

7. The development is OK. I think it is more stable than other platforms.

8. In go, the outcome is determined by the number of intersections. The intersection is the result of the intersection of 19 horizontal lines and 19 vertical lines in the chessboard × 19 = 361 points. In technical terms, these points are called "Mu" or "Zi". The last side with more mesh or sub number wins. But generally speaking, the black side should first paste 7.5 mesh to the white side to balance the advantages of the first hand, that is to say, the white side should add 7.5 mesh to compare with the black side. Note that the meanings of "Mu" and "Zi" are different from those mentioned above. Here, "Mu" and "Zi" refer to two different methods of calculating the outcome. Either method can be used, and the meaning is the same

let's first talk about the calculation method of "item": the difference between the number of items on both sides, such as 180.5 items on the black side and 180.5 items on the white side, is that the white side wins 7.5 items, because the black side has to post 7.5 items first

let's talk about the calculation method of "sub": half of the intersection point is 180.5 + 3 + 3 / 4 (half of 7.5 mesh). If one party wins by more than this number, the number of sub winning is the difference between the number of sub winning party and 180.5 + 3 + 3 / 4, which is the same as the above example, that is, white party wins 3 + 3 / 4.

9. In the actual development, we often encounter some situations like this,
(1) in the case of sudden high concurrency, when the server is under great pressure and calls some methods for more than 100ms and does not respond, we should automatically reject the service instead of blocking until the server crashes, It can be regarded as a disguised service degradation
(2) for the unpredictable code that may have deadlock, add time threshold limit to avoid unlimited resource competition
(3) for the unpredictable code that may have deadlock, add time threshold monitoring, Avoid dead cycle deterioration

some mature open source frameworks generally have the function of timeout response, such as
search framework: Lucene, Solr, elasticsearch,
RPC framework: Dubbo, thrift,
service coordination framework: zookeeper, etc.
if we want to add this function, what should we do
in fact, it's not difficult to add a timing function before and after the method call. If the threshold is exceeded, the thread should be terminated actively and the exception code should be thrown. Of course, in order not to affect the operation of the main service, this code should run independently in a sub thread, rather than coupled in the main thread. The idea is roughly the same. Of course, in order not to build a wheel repeatedly, we suggest to use Google's open source guava toolkit, which provides many useful functions, including the automatic termination of timeout method introced this time, and some functions to limit network traffic or the number of visits within a specified period of time, You can see guava's documentation for yourself<
timelimiter is an interface. There are two subclasses below,
faketimelimiter, which is often used to limit time-out debugging ring debugging.
simpletimelimiter is often used in formal methods, which call method time-out, that is, throw exception.
this paper focuses on the use of simpletimelimiter, There are mainly two methods in this class:
(1) newproxy implements timeout interception through JDK dynamic proxy and callwithtimeout
(2) callwithtimeout implements timeout interception through callable callback
the difference between the two methods lies in that the strategy implemented through proxy can be applied to every called method in this class, The implementation of timeout interception
and the implementation strategy through callback is applicable to the implementation of timeout interception only for a certain code block or method
introce the latest guava package through Maven:
java code

& lt; dependency> < br /> < groupId> com.google.guava</ groupId> < br /> < artifactId> guava</ artifactId> < br /> < version> 19.0</ version> < br /> </ dependency> <
A: Interception Based on proxy mode:
since guava uses JDK dynamic proxy to implement AOP interception, it requires that the proxy class must have an interface implementation, so it's a little troublesome to use.
we need to define an interface first, then define the implementation class, and rewrite the method to be called:
b: callback based usage, which is relatively simple, Because there is no need to use proxy mode,
both methods can implement method call timeout interruption, proxy mode is suitable for class level method timeout interruption, while callback based mode is more suitable for any single method.