Bitcoin port 6667

Bitcoin uses a simple broadcast network to propagate transactions and blocks. All communications are done over TCP. Bitcoin is fully able to use ports other than 8333 via the -port parameter. IPv6 is suported with Bitcoind/Bitcoin-Qt v0.7.

Messages

• version - Information about program version and block count. Exchanged when first connecting.
• verack - Sent in response to a version message to acknowledge that we are willing to connect.
• addr - List of one or more IP addresses and ports.
• inv - "I have these blocks/transactions: ..." Normally sent only when a new block or transaction is being relayed. This is only a list, not the actual data.
• getdata - Request a single block or transaction by hash.
• getblocks - Request an inv of all blocks in a range.
• getheaders - Request a headers message containing all block headers in a range.
• tx - Send a transaction. This is sent only in response to a getdata request.
• block - Send a block. This is sent only in response to a getdata request.
• headers - Send up to 2, 000 block headers. Non-generators can download the headers of blocks instead of entire blocks.
• getaddr - Request an addr message containing a bunch of known-active peers (for bootstrapping).
• submitorder, checkorder, and reply - Used when performing an IP transaction.
• alert - Send a network alert.
• ping - Does nothing. Used to check that the connection is still online. A TCP error will occur if the connection has died.

More information and in-depth technical information is in the Protocol Specification.

Connection

To connect to a peer, you send a version message containing your version number, block count, and current time. The remote peer will send back a verack message and his own version message if he is accepting connections from your version. You will respond with your own verack if you are accepting connections from his version.

The time data from all of your peers is collected, and the median is used by Bitcoin for all network tasks that use the time (except for other version messages).

You then exchange getaddr and addr messages, storing all addresses that you don't know about. addr messages often contain only one address, but sometimes contain up to 1000. This is most common at the beginning of an exchange.