Difference between revisions of "Protocol FAQ"

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(Copypasta from the protocol encryption page for login sequence)
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See [[Authentication]] for communication with minecraft.net
See [[Authentication]] for communication with minecraft.net
{{Warning|The information below is out-of-date and needs updating for 1.7}}  
{{Warning|Information might not be totally up to date}}  
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#Client connects to server
#Client connects to server
#'''C->S''' 0x02 handshake
#'''C->S''' : Handshake State=2
#'''S->C''' 0xFD encryption request - server sends its public key and 4 random bytes
#'''C->S''' : Login Start
#Client generates symmetric key (shared secret)
#'''S->C''' : Encryption Key Request
#Client authenticates via session.minecraft.net
#(Client Auth)
#Client encrypts these 4 bytes with the servers public key.
#'''C->S''' : Encryption Key Response
#'''C->S''' 0xFC encryption response - client encrypts shared secret with server's public key and sends along with encrypted 4 bytes
#(Server Auth, Both enable encryption)
#Server checks that the encrypted bytes match
#'''S->C''' : Login Success
#Server decrypts shared secret with its private key
#Server checks player authenticity via session.minecraft.net
#'''S->C''' 0xFC encryption response - empty payload meaning two zero length byte arrays and two zero shorts
#Server enables AES stream encryption
#Client enables AES stream encryption
#'''C->S''' 0xCD - Payload of 0 (byte)
#'''S->C''' : Either kicks (invalid login) or sends a login response
#'''S->C''' : Sends chunks and entities
#'''S->C''' : Sends chunks and entities
#'''S->C''' : Sends spawn position
#'''S->C''' : Sends spawn position

Revision as of 04:37, 11 March 2014

People very, very often have questions regarding the Minecraft Modern Protocol, so we'll try to address some of the most common ones on this document. If you're still having trouble, join us on IRC, channel #mcdevs on irc.freenode.net.

Is the protocol documentation complete?

Depending on your definition, yes! All packet types are known and their layout documented. Some finer details are missing, but everything you need to make functional programs is present. We have a script that monitors for new versions of the client and notifies us, allowing us to quickly document new packets.

What's the normal login sequence for a client?

See Authentication for communication with minecraft.net

Warning.png Information might not be totally up to date

The recommended login sequence looks like this, where C is the client and S is the server:

  1. Client connects to server
  2. C->S : Handshake State=2
  3. C->S : Login Start
  4. S->C : Encryption Key Request
  5. (Client Auth)
  6. C->S : Encryption Key Response
  7. (Server Auth, Both enable encryption)
  8. S->C : Login Success
  9. S->C : Sends chunks and entities
  10. S->C : Sends spawn position
  11. S->C : Sends inventory [Need to verify this since inventory changed] (beta 1.1_02: looks like Window items with type=0, then a Set slot with window id = -1 and slot = -1)
  12. S->C : Tell the client they're ready to spawn by sending a position + look packet.
  13. C->S : Sends a position + look packet to confirm the spawn position

I think I've done everything right, but…

…my player isn't spawning!

After sending the common-sense packets (Handshake, Login, Inventory, Compass and Chunks) you need to finally send the player their initial position for them to leave the "Loading Map" screen.

Note that if the following steps are taken, a Minecraft client will spawn the player:

1) Do Handshake (See Protocol Encryption)
2) Send Spawn Position PDU
3) Send Player Position and Look PDU

While the above steps are sufficient for Minecraft 1.4.5, it is good form to send PDUs that inform the client about the world around the player before allowing the player to spawn.

…my client isn't receiving complete map chunks!

Main article: How to Write a Client

The standard Minecraft server sends full chunks only when your client is sending player status update packets (any of Player (0x0A) through Player Position & Look (0x0D)).

…all connecting clients spasm and jerk uncontrollably!

For newer clients, your server needs to send 49 chunks ahead of time, not just one. Send a 7x7 square of chunks, centered on the connecting client's position, before spawning them.