Is it possible for a valid block to be added to an invalid one, and have it accepted by another client?


With the client, the node accepts a block only after none of the verification steps fail.

Each block in the block*chain* is linked to a prior block with a reference to that prior block's hash.

So take the case where a node sees the longest chain ending at height 1,000. Then it receives a block 1,001. The client will then verify that the hash that block gives for block 1,000 truly matches the hash the client already knows about (from the longest chain) for block 1,000. It won't match, so this 1,001 doesn't extend off of the block 1,000 the client already knows about.

And since the client doesn't have knowledge of any other block 1,000 with that hash that 1,0001 purports to extend from, the client will not accept block 1,001 -- there is no link tying it to any previously received...

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I would like to download (and access) as much blocks as possible - including stale (extinct) blocks, orphans blocks and invalid blocks.
I have 0.11 official client.
My node is already synchronized but I can re-sync for that.
As I understand thanks to header-first IBD method (and maybe some other improvement) introduced in 0.10.0:

I have as few as possible stale blocks (only those downloaded after IBD) I don't have invalid blocks I don't have orphans as they were not materialized because they would be waiting for missing parents(?)

How can I download as much of them as possible?

Besides of downloading blocks what rpc calls should I use to query those blocks from local blockchain?

getbestblock will let me iterate using getblock from the most recent block all the way down to genesis I can also getblock to iterate starting from genesis block

None of above gives access to stale or invalid. Orphaned were not materialized, correct?, so I'm not...

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You may have noticed that it takes longer to reject an invalid password than to accept a valid one. There are a few reasons for this.

First of all, it simply takes longer to confirm that a password is invalid.

Your local computer retains a password cache. This password cache improves performance of local authentication operations, such as unlocking a workstation. If you unlock the workstation with the same password you used to log on, then the password is assumed to be good. This allows the workstation to unlock quickly. Without the password cache, unlocking the workstation would require going back to the domain controller to validate the password, which for slow network connections, can take a very long time. In fact, you might not have any network connection at all (an extreme case of slow), say because you've taken your laptop on the road and are not connected to the corporate network any more. In that case, without the password cache, it would be impossible for...

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1. Do transactions ever time out if not accepted into the block chain?

e.g. if I create a transaction today, and it happens to be invalid, is it possible it will unexpectedly get accepted, e.g. with a later release of the bitcoin block chain code that has policy changes, maybe in x years time? (assuming transaction this would have to be accepted by miner *and* the block chain code)

> Usually your bitcoin core will rebroadcast transactions which have not confirmed. It will do this indefinitely unless you remove the tx from your wallet.

Transactions only need to be mined by ONE miner. Most nodes block non-standard transactions, and won't pass them on, meaning miners won't hear about it. The only way to circumvent this is to broadcast your transaction directly to a miner who mines non-standard transactions, he may include it in a block. Eligius do this, and in fact, I have the % of non-standard multisig transactions here:...

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I'm working on a Cocoa-Touch app, it uses CoreData and has some NSPersistentObject subclasses generated by the XCode model editor.

I've noticed that recently, when saving the context I get an error which has as user info the following part:

(gdb) po ui { "Dangling reference to an invalid object." = ; NSAffectedObjectsErrorKey = ; NSLocalizedDescription = "Operation could not be completed. (Cocoa error 1550.)"; NSValidationErrorKey = ; NSValidationErrorObject = ; NSValidationErrorValue = { }; }

There are on other keys in the user info dictionary.

All the dumps I get are valid objects, I've verified them all.

NSValidationErrorObject is an object which has an NSSet which contains objects of types dumped in NSAffectedObjectsErrorKey and NSValidationErrorValue. But all these objects are valid.

Furthermore, this happens randomly, sometimes it happens, sometimes not, and sometimes the list dumped in NSValidationErrorValue is longer, sometimes...

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This page is not complete.

Sending data is not enough — we also need to make sure that the data users fill out in forms is in the correct format we need to process it successfully, and that it won't break our applications. We also want to help our users to fill out our forms correctly and don't get frustrated when trying to use our apps. Form validation helps us achieve these goals — this article tells you what you need to know.

What is form validation?

Go to any popular site with a registration form, and you will notice that they give you feedback when you don't enter your data in the format they are expecting. You'll get messages like:

"This field is required" (you can't leave this field blank) "Please enter your phone number in the format xxx-xxxx" (it wants three numbers followed by a dash, followed by four numbers) "Please enter a valid e-mail address" (the thing you've entered doesn't look like a valid e-mail address) "Your password needs...
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This error means that the timestamp extractor of your Kafka Streams application failed to extract a valid timestamp from a record. Typically, this points to a problem with the record (e.g., the record does not contain a timestamp at all), but it could also indicate a problem or bug in the timestamp extractor used by the application.

When does a record not contain a valid timestamp:

If you are using the default FailOnInvalidTimestamp (for v0.10.0 and v0.10.1 ConsumerRecordTimestampExtractor), it is most likely that your records do not carry an embedded timestamp (embedded record timestamps got introduced in Kafka’s message format in Kafka 0.10). This might happen, if for example, you consume a topic that is...
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It depends on the subnet of the IP address in question. In general, the first and last addresses in a subnet are used as the network identifier and broadcast address, respectively. All other addresses in the subnet can be assigned to hosts on that subnet.

For example, IP addresses of networks with subnet masks of at least 24 bits ending in .0 or .255 can never be assigned to hosts. Such "last" addresses of a subnet are considered "broadcast" addresses and all hosts on the corresponding subnet will respond to it.

Theoretically, there could be situations where you can assign an address ending in .0: for example, if you have a subnet like, you are allowed to assign a host the address It could create confusion though, so it's not a very common practice.

In your example with subnet (22 bit subnet mask)

means subnet ID, a host address range from to and a broadcast...

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General Information


The MikroTik HotSpot Gateway enables providing of public network access for clients using wireless or wired network connections.

HotSpot Gateway features:

authentication of clients using local client database, or RADIUS server accounting using local database, or RADIUS server Walled-garden system (accessing some web pages without authorization)

Quick Setup Guide

The most noticeable difference in user experience setting up HotSpot system in version 2.9 from the previous RouterOS versions is that it has become in order of magnitude easier to set up a correctly working HotSpot system.

Given a router with two interfaces: Local (where HotSpot clients are connected to) and Public, which is connected to the Internet. To set up HotSpot on the Local interface:

first, a valid IP config is required on both interfaces. This can be done with /setup command. In this example we will assume the...
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Think about this: a miner A that withhold the block data (but not the header) does not get any direct additional income. Only if another miner B finds a block within the 10 second window and the block has no transactions because the block transactions were never received by X, then A could take those transaction fees if he is lucky enough to mine the next block, and assuming the remaining existent transactions in the pool do not provide equal profit. But if the block is saturated the remaining transactions, on average, should have approximately the same amount of fees. So nothing is gained.

As an example, assuming the current state of Bitcoin. Let $ 40 (USD) be the average tx fees per block. Let the probability of a collision in a 10 seconds windows be 1.6%. if miner A has 20 % of the hashing rate, and 1 every two blocks has transaction fees which are 50% higher than the next block fees, then A would get an average of 40/2/5= 4 (USD) of additional income per block by not...

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4. Memcheck: a memory error detector

To use this tool, you may specify --tool=memcheck on the Valgrind command line. You don't have to, though, since Memcheck is the default tool.

Memcheck is a memory error detector. It can detect the following problems that are common in C and C++ programs.

Accessing memory you shouldn't, e.g. overrunning and underrunning heap blocks, overrunning the top of the stack, and accessing memory after it has been freed.

Using undefined values, i.e. values that have not been initialised, or that have been derived from other undefined values.

Incorrect freeing of heap memory, such as double-freeing heap blocks, or mismatched use of malloc/new/new[] versus free/delete/delete[]

Overlapping src and dst pointers in memcpy and related functions.

Passing a fishy (presumably negative) value to the size parameter of a memory allocation function.

Memory leaks.

Problems like these...

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Understand the basic requirements of a valid will before you rely on it to wrap up the estate.

As an executor, before you start deciphering a will in preparation for settling an estate, you should take a moment to consider whether the will is valid. The final word on validity will be issued by the probate court if you go through formal probate proceedings. But it's good to be confident that the will is a legally binding document before you begin following its instructions. (For tips on wrapping up an estate if no valid will can be found, see How Is an Estate Settled If There's No Will: Intestate Succession)

First off, it's important to understand that certain circumstances can affect the will:

Family changes -- for example, the will maker's divorce or marriage -- can have dramatic legal effects on the terms of a valid will. Wills generally cannot dispose of property that's held in joint tenancy or in a living trust, or for which a beneficiary has been named...
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The Government envisions providing good governance by establishing a COMMITTED, ACCOUNTABLE, RESPONSIVE, INSPIRING, NATIONALIST, GENUINE Government - CARING Government. eProcurement is one of the vehicles that are being gainfully used in reaching the goal of CARING governance. is a comprehensive e-infrastructure that will help the government and the citizens realize the vision of fuelling growth via profitable B2B eCommerce, providing a robust, proven platform used by the largest companies in India and the world. It enables trade between companies of different sizes, platforms and locations. To this end, provides eTendering services through

The Tender Management Software helps buyers and suppliers to reduce the cycle time, unnecessary paper work, waiting in long queues and simultaneously maintain the transparency in the entire process. eProcurement will be utilised by all GoAP departments...

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