Bitcoin addr message
Structure to be expanded in the future… see script. The block message is sent in response to a getdata message which requests transaction information from a block hash. To calculate the hash, only two chunks need to be processed by the SHA algorithm. Since the nonce field is in the second chunk, the first chunk stays constant during mining and therefore only the second chunk needs to be processed. However, a Bitcoin hash is the hash of the hash, so two SHA rounds are needed for each mining iteration.
See Block hashing algorithm for details and an example. The getaddr message sends a request to a node asking for information about known active peers to help with finding potential nodes in the network.
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The response to receiving this message is to transmit one or more addr messages with one or more peers from a database of known active peers. The typical presumption is that a node is likely to be active if it has been sending a message within the last three hours. The mempool message sends a request to a node asking for information about transactions it has verified but which have not yet confirmed. The response to receiving this message is an inv message containing the transaction hashes for all the transactions in the node's mempool.
It is specified in BIP Since BIP 37 , if a bloom filter is loaded, only transactions matching the filter are replied. This message was used for IP Transactions. As IP transactions have been deprecated, it is no longer used.
An error in transmission is presumed to be a closed connection and the address is removed as a current peer. The pong message is sent in response to a ping message. In modern protocol versions, a pong response is generated using a nonce included in the ping. These messages are related to Bloom filtering of connections and are defined in BIP See below for a description of the Bloom filter algorithm and how to select nHashFuncs and filter size for a desired false positive rate.
Upon receiving a filterload command, the remote peer will immediately restrict the broadcast transactions it announces in inv packets to transactions matching the filter, where the matching algorithm is specified below. The flags control the update behaviour of the matching algorithm. The data field must be smaller than or equal to bytes in size the maximum size of any potentially matched object. The given data element will be added to the Bloom filter. A filter must have been previously provided using filterload.
This command is useful if a new key or script is added to a clients wallet whilst it has connections to the network open, it avoids the need to re-calculate and send an entirely new filter to every peer though doing so is usually advisable to maintain anonymity. After a filter has been set, nodes don't merely stop announcing non-matching transactions, they can also serve filtered blocks. A filtered block is defined by the merkleblock message and is defined like this:. After a merkleblock , transactions matching the bloom filter are automatically sent in tx messages.
A guide to creating a bloom filter, loading a merkle block, and parsing a partial merkle block tree can be found in the Developer Examples. Note: Support for alert messages has been removed from bitcoin core in March Read more here. An alert is sent between nodes to send a general notification message throughout the network.
If the alert can be confirmed with the signature as having come from the core development group of the Bitcoin software, the message is suggested to be displayed for end-users. Attempts to perform transactions, particularly automated transactions through the client, are suggested to be halted.
- Wireshark · Display Filter Reference: Bitcoin protocol.
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The text in the Message string should be relayed to log files and any user interfaces. The payload is serialized into a uchar to ensure that versions using incompatible alert formats can still relay alerts among one another. The current alert payload format is:. Upon receipt of this message, the node is be permitted, but not required, to announce new blocks by headers command instead of inv command.
The value represents a minimal fee and is expressed in satoshis per bytes. Upon receipt of a "feefilter" message, the node will be permitted, but not required, to filter transaction invs for transactions that fall below the feerate provided in the feefilter message interpreted as satoshis per kilobyte. The fee filter is additive with a bloom filter for transactions so if an SPV client were to load a bloom filter and send a feefilter message, transactions would only be relayed if they passed both filters.
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Primary code and documentation
Only to be used in getdata message. Indicates the reply should be a merkleblock message rather than a block message; this only works if a bloom filter has been set. See BIP 37 for more info. Indicates the reply should be a cmpctblock message. See BIP for more info. Hash of a block with witness data. The reference to a Merkle tree collection which is a hash of all transactions related to this block.
A timestamp recording when this block was created Will overflow in . The nonce used to generate this block… to allow variations of the header and compute different hashes. As encoded in tx messages. The short transaction IDs calculated from the transactions which were not provided explicitly in prefilledtxn. As defined by PrefilledTransaction definition, above.
Used to provide the coinbase transaction and a select few which we expect a peer may be missing. List of CompactSizes. Differentially encoded. Node random nonce, randomly generated every time a version packet is sent. This nonce is used to detect connections to self. User Agent 0x00 if string is 0 bytes long. Whether the remote peer should announce relayed transactions or not, see BIP See BIP Never formally proposed as a BIP , and discontinued.