Session
The minecraft client and server communicate with minecraft.net to validate player sessions. This page describes some of the operations.
Contents
Login
To log the player in, the official launcher sends an HTTPS POST (GET appears to suffice as well) request to:
https://login.minecraft.net
with the postdata:
?user=<username>&password=<password>&version=<launcher version>
and a "application/x-www-form-urlencoded" Content-Type header.
After migrating to Mojang accounts, email address is used instead of username, but the procedure stays the same.
The current launcher version is "13" (for new launcher it's "14"), sending a value lower than 12 will cause the server to return "Old version", however you can send any large number and it will return as expected. If the login succeeded, it will return 5 ':' delimited values.
1343825972000:deprecated:SirCmpwn:7ae9007b9909de05ea58e94199a33b30c310c69c:dba0c48e1c584963b9e93a038a66bb98
- current version of the game files (not the launcher itself). This is a unix timestamp which the launcher compares to the ~/.minecraft/bin/version file.
- Previously contained a download ticket for requesting new versions of minecraft.jar from the server. Now contains only "deprecated".
- case-correct username. For mojang accounts, the user's actual username is returned here instead of the email used to log in.
- sessionId - a unique ID for your current session.
- UID - currently unused, introduced near August 8th, 2012. Grum says this is the unique ID for the user, potentially for changing Minecraft names in future.
If the request is missing a parameter, the server will return "Bad response". If the login information is incorrect, the server will return "Bad login". If the login information is correct but the account isn't premium, the server will return "User not premium". If your minecraft.net account has been migrated to a Mojang account but you're logging in with your minecraft.net username the server will return "Acount migrated, use e-mail".
Login 1.6
In minecraft 1.6 there is a new launcher, which uses a different method of authenticating users:
The client authenticates by doing:
POST https://authserver.mojang.com/authenticate
with (json encoded)
{ "agent":{"name":"Minecraft","version":1}, "username":"account@mailserver.com", "password":"xxxxxxx", "clientToken":"dddddddd-aaaa-bbbb-cccc-111111111111" }
The authserver responds with:
{ "accessToken":"99999999999999999999999999999999", "clientToken":"dddddddd-aaaa-bbbb-cccc-111111111111", "availableProfiles":[ {"id":"55555555555555555555555555555555","name":"MOJANGNAME"} ], "selectedProfile":{"id":"55555555555555555555555555555555","name":"MOJANGNAME"} }
then the client checks on mcoapi with:
GET https://mcoapi.minecraft.net/mco/available
with this cookie
Cookie: sid=token:99999999999999999999999999999999:55555555555555555555555555555555;user=MOJANGNAME;version=1.6.2
When connecting to a server, the client first establishes an encrypted session with the server, then does:
GET http://session.minecraft.net/game/joinserver.jsp? user=MOJANGNAME& sessionId=token%3A99999999999999999999999999999999%3A55555555555555555555555555555555& serverId=-6666666666666666666666666666666666666666
the server verifies if the user did call joinserver by doing:
GET http://session.minecraft.net/game/checkserver.jsp? user=MOJANGNAME& serverId=-6666666666666666666666666666666666666666
Updating
To update, the launcher downloads files from
http://s3.amazonaws.com/MinecraftDownload/
It takes the unix timestamp from the login request and stores it in ~/.minecraft/bin/version
The following files are downloaded from /MinecraftDownload/ in this exact order:
- lwjgl.jar
- jinput.jar
- lwjgl_util.jar
- minecraft.jar
And then the natives.jar appropriate for the following operating systems: windows, linux, macosx, and solaris
- <os-from-list-above>_natives.jar.lzma
When downloading minecraft.jar, GET variables are set as follows: ?user=foo&ticket=deprecated, although they seem unnecessary to successfully downloading the file.
Furthermore, the downloaded files are all verified via MD5 which is sent via ETag by the server on the page for each file.
Further resources are stored in /MinecraftResources. Loading /MinecraftResources provides an XML formatted list of resources, some of which are downloaded by Minecraft and not the launcher.
Keep-alive
Every 6000 ticks, the client sends an HTTPS request to
https://login.minecraft.net/session?name=<username>&session=<session id>
The client discards the server's response.
Snoop
Every 15 minutes, minecraft sends a HTTP POST request giving stats. This can be disabled in server.properties
- client: http://snoop.minecraft.net/client?version=1
- server: http://snoop.minecraft.net/server?version=1
Field | Client | Server | Example | Notes |
---|---|---|---|---|
applet | Yes | No | true
|
|
avg_rec_packet_count | No | Yes | 0
|
|
avg_rec_packet_size | No | Yes | 0
|
|
avg_sent_packet_count | No | Yes | 6
|
|
avg_sent_packet_size | No | Yes | 44
|
|
avg_tick_ms | No | Yes | 3
|
|
client_brand | Yes | No | vanilla
|
via ClientBrandRetriever.getClientModName()
|
cpu_cores | Yes | Yes | 2
|
via Runtime.getRuntime().availableProcessors()
|
dedicated | No | Yes | true
|
|
display_frequency | Yes | No | 60
|
via org.lwjgl.opengl.Display.getDisplayMode().getFrequency()
|
display_type | Yes | No | windowed
|
windowed or fullscreen
|
fps | Yes | No | 60
|
|
gl_caps[key] | Yes | No | varies by key | via org.lwjgl.opengl.GLContext.getCapabilities().GL_ARB_key
|
gl_max_texture_size | Yes | No | 8192
|
|
gui_state | No | Yes | disabled
|
enabled or disabled
|
gui_supported | No | Yes | headless
|
via java.awt.GraphicsEnvironment.isHeadless() (headless or supported )
|
java_version | Yes | Yes | 1.6.0_24
|
via System.getProperty("java.version")
|
jvm_arg[n] | Yes | Yes | -Xms2800M
|
via java.lang.management.ManagementFactory.getRuntimeMXBean().getInputArguments() (-X args only)
|
jvm_args | Yes | Yes | 2
|
see above |
memory_free | Yes | Yes | 2429082024
|
via Runtime.getRuntime().freeMemory()
|
memory_max | Yes | Yes | 2813722624
|
via Runtime.getRuntime().maxMemory()
|
memory_total | Yes | Yes | 2813722624
|
via Runtime.getRuntime().totalMemory()
|
opengl_vendor | Yes | No | NVIDIA Corporation
|
via GL11.glGetString(GL_VENDOR)
|
opengl_version | Yes | No | 3.3.0 NVIDIA 302.17
|
via GL11.glGetString(GL_VERSION)
|
os_architecture | Yes | Yes | amd64
|
via System.getProperty("os.arch")
|
os_name | Yes | Yes | Linux
|
via System.getProperty("os.name")
|
os_version | Yes | Yes | 3.2.0-3-amd64
|
via System.getProperty("os.version")
|
players_current | No | Yes | 0
|
|
players_max | No | Yes | 20
|
|
players_seen | No | Yes | 4
|
counts files in world/players |
server_brand | No | Yes | vanilla
|
via getServerModName() (hardcoded to "vanilla", overwritten by bukkit et al)
|
singleplayer | No | Yes | false
|
whether or not the server is running to support a singleplayer session |
snooper_count | Yes | Yes | 0
|
how many times the snooper has reported so far |
snooper_token | Yes | Yes | dfe921ac-0293-4e42-8d99-1316cdd626d8
|
via java.util.UUID.randomUUID().toString() (unique per program launch)
|
texpack_name | Yes | No | Default
|
|
texpack_resolution | Yes | No | 16
|
|
uses_auth | No | Yes | true
|
corresponds to online-mode in server.properties
|
version | Yes | Yes | 1.4.2
|
|
vsync_enabled | Yes | No | true
|
|
whitelist_count | No | Yes | 0
|
|
whitelist_enabled | No | Yes | false
|
|
world[n][chunks_loaded] | No | Yes | 978
|
|
world[n][difficulty] | No | Yes | 1
|
|
world[n][dimension] | No | Yes | 0
|
|
world[n][generator_name] | No | Yes | default
|
|
world[n][generator_version] | No | Yes | 1
|
|
world[n][hardcore] | No | Yes | false
|
|
world[n][height] | No | Yes | 256
|
|
world[n][mode] | No | Yes | SURVIVAL
|
|
worlds | No | Yes | 3
|
Joining a Server
See Protocol Encryption for details on encrypting connections.
Client operation
- Client connects to server
- Client sends a 0x02 handshake containing the current player name
- Client receives an 0xFD encryption request with the server's public key and four verification bytes.
- Client generates a symmetric key.
- Client sends a HTTP request to
http://session.minecraft.net/game/joinserver.jsp?user=<username>&sessionId=<session id>&serverId=<server hash>
- Note: Case-corrected username is used here, not the Mojang account username.
- If the response is OK then continue, otherwise stop
- Client sends 0xFC encryption response - client encrypts shared secret and verification token with the server's public key
- Server checks validity and sends 0xFC encryption response with two empty arrays
- Both sides enable AES/CFB2 encryption using the shared secret generated by the client
- Client sends 0xCD client status with a payload of 0 (ready to spawn)
- Server sends 0x01 login
- ... receive map chunks, etc...
Server operation
- Server generates a 1024-bit RSA keypair.
- ...
- Server answers TCP connection request and receives a 0x02 handshake from the client.
- Server sends 0xFD encryption request with its public key and a verification token.
- Server receives 0xFC encryption response from client and decrypts the shared secret.
- Server verifies the validity of the verification token. If this isn't verified, it kicks the client.
- Server sends a HTTP request to
http://session.minecraft.net/game/checkserver.jsp?user=<username>&serverId=<server hash>
- If it returns YES then the client is authenticated and allowed to join. Otherwise the client will/should be kicked with “Failed to verify username!”
- Server sends a 0xFC encryption response packet with two empty arrays.
- Both sides enable AES/CFB2 encryption.
- Server receives 0xCD client status with a payload of , indicating "ready to spawn"
- Server sends 0x01 login
- ... send map chunks, etc...