[[Category RS2]]
This page is an attempt to document the protocol and other relevant information for client build 666.

== '''Handshakes''' ==
This section documents the handshake packets sent from the client to the server.

{| class="wikitable" style="text-align: center"
|-
! Name
! Opcode
! Length
! Fields
! Description
|-
! Init Game Connection
| 14
| 0
| None
| Indicates that the connection is for logging the client into the lobby or game.
|-
! Init Update Connection
| 15
| 4
| style="text-align: left" | 
* client_build: int32
| Indicates that the connection is for streaming the game's resources to the client.
|-
! Game Login
| 16
| Variable (short)
| style="text-align: left" | 
* client_build: int32
* reconnecting: int8
* rsa_block_len: int16
* RSA block
** block_header: int8
** xtea_key: int32[4]
** unknown: int64
** password: cstring
** server_session_key: int64
** client_session_key: int64
* XTEA block
** username: cstring
** unknown: int8
** screen_type: int8
** screen_width: int16
** screen_height: int16
** multisampling_level: int8
** uid: int8[24]
** settings: cstring
** affiliate_id: int32
** preferences_length: int8
** preferences_data: int8[preferences_length]
** System info
*** sysinfo_version: int8
*** os_type: int8
*** is_64bit: int8
*** os_version: int8
*** java_vendor: int8
*** java_release: int8
*** java_version: int8
*** java_update: int8
*** unsigned: int8
*** heap_size: int16
*** processor_count: int8
*** total_memory: int24
*** unknown: int16
*** unknown: int8
*** unknown: int8
*** unknown: int8
*** unknown: jstring
*** unknown: jstring
*** unknown: jstring
*** unknown: jstring
*** unknown: int8
*** unknown: int16
** unknown: int32
** user_flow: int64
** has_additional_info: int8
*** additional_info: cstring
** has_jagtheora: int8
** using_javascript: int8
** archive_checksums: int32[36]
| Attempts to login to the game server.
|-
! Handshake 17
| 17
| 0
| None
| Not used but present in the client.
|-
! Lobby Login
| 19
| Variable (short)
| style="text-align: left" | 
* client_build: int32
* rsa_block_len: int16
* RSA block
** block_header: int8
** xtea_key: int32[4]
** unknown: int64
** password: cstring
** server_session_key: int64
** client_session_key: int64
* XTEA block
** username: cstring
** game_id: int8
** language: int8
** uid: int8[24]
** settings: cstring
** affiliate_id: int32
** archive_checksums: int32[36]
| Attempts to login to the lobby server.
|-
! Create Account
| 22
| Variable (short)
| style="text-align: left" |
* client_build: int32
* rsa_block_len: int16
* RSA block
** block_header: int8
** xtea_key: int32[4]
** padding: int32[10]
** unknown: int16
* XTEA block
** email: cstring
** affiliate_id: int16
** password: cstring
** user_flow: int64
** language: int8
** game_id: int8
** uid: int8[24]
** has_additional_info: int8
*** additional_info: cstring
** age: int8
** email_updates: int8
** padding: int8[7]
| Attempts to create an account with the given information.
|-
! Handshake 23
| 23
| 4
| None
| Not used but present in the client.
|-
! Handshake 24
| 24
| Variable (byte)
| None
| Not used but present in the client.
|-
! Finished Advertisement
| 26
| 0
| None
| Notifies the server that the client has finished viewing the advertisement.
|-
! Handshake 27
| 27
| 0
| None
| Not used but present in the client.
|-
! Check Email
| 28
| Variable (short)
| style="text-align: left" |
* client_build: int32
* rsa_block_len: int16
* RSA block
** block_header: int8
** xtea_key: int32[4]
** padding: int32[10]
** unknown: int16
* XTEA block
** email: cstring
** language: int8
** padding: int8[7]
| Asks the server to verify whether the given email can be used to create an account.
|-
! Init Social Network Connection
| 29
| Variable (short)
| style="text-align: left" |
* client_build: int32
* reconnecting: int8 (if game server connection)
* rsa_block_len: int16
* RSA block
** block_header: int8
** xtea_key: int32[4]
** social_network_id: int8
** unknown: int16
** language: int8
** affiliate_id: int32
** padding: int32[6]
** client_session_key: int64
** game_id: int8
** unknown: int8
| Initializes a connection using a social network.
|-
! Social Network Login
| 30
| Variable (short)
| style="text-align: left" |
* Game login
** XTEA block
*** unknown: int8
*** screen_type: int8
*** screen_width: int16
*** screen_height: int16
*** multisampling_level: int8
*** uid: int8[24]
*** settings: cstring
*** affiliate_id: int32
*** preferences_length: int8
*** preferences_data: int8[preferences_length]
*** System info
**** sysinfo_version: int8
**** os_type: int8
**** is_64bit: int8
**** os_version: int8
**** java_vendor: int8
**** java_release: int8
**** java_version: int8
**** java_update: int8
**** unsigned: int8
**** heap_size: int16
**** processor_count: int8
**** total_memory: int24
**** unknown: int16
**** unknown: int8
**** unknown: int8
**** unknown: int8
**** unknown: jstring
**** unknown: jstring
**** unknown: jstring
**** unknown: jstring
**** unknown: int8
**** unknown: int16
*** unknown: int32
*** user_flow: int64
*** has_additional_info: int8
**** additional_info: cstring
*** has_jagtheora: int8
*** using_javascript: int8
*** archive_checksums: int32[36]
* Lobby login
** XTEA block
*** game_id: int8
*** language: int8
*** uid: int8[24]
*** settings: cstring
*** affiliate_id: int32
*** archive_checksums: int32[36]
| Attempts to login to either the game or lobby server using a social network.
|-
|}

== '''Game Protocol''' ==

=== '''Packets''' ===
This section documents the packets sent between the client and server during normal gameplay.

==== '''Client-to-Server''' ====
{| class="wikitable" style="text-align: center"
|-
! Name
! Opcode
! Length
! Fields
! Description
|-
! Packet 0
| 0
| 0
| 
| 
|-
! Packet 1
| 1
| 7
| 
| 
|-
! Packet 2
| 2
| Variable (byte)
| 
| 
|-
! Packet 3
| 3
| 8
| 
| 
|-
! Packet 4
| 4
| 3
| 
| 
|-
! Packet 5
| 5
| Variable (byte)
| 
| 
|-
! Packet 6
| 6
| 15
| 
| 
|-
! Packet 7
| 7
| 8
| 
| 
|-
! Packet 8
| 8
| 6
| 
| 
|-
! Packet 9
| 9
| Variable (byte)
| 
| 
|-
! Packet 10
| 10
| 3
| 
| 
|-
! Packet 11
| 11
| 8
| 
| 
|-
! Packet 12
| 12
| Variable (byte)
| 
| 
|-
! Packet 13
| 13
| Variable (byte)
| 
| 
|-
! Packet 14
| 14
| 3
| 
| 
|-
! Packet 15
| 15
| 4
| 
| 
|-
! Packet 16
| 16
| 7
| 
| 
|-
! Packet 17
| 17
| 8
| 
| 
|-
! Packet 18
| 18
| 1
| 
| 
|-
! Packet 19
| 19
| Variable (byte)
| 
| 
|-
! Packet 20
| 20
| 4
| 
| 
|-
! Packet 21
| 21
| 2
| 
| 
|-
! Packet 22
| 22
| Variable (byte)
| 
| 
|-
! Packet 23
| 23
| 7
| 
| 
|-
! Packet 24
| 24
| 7
| 
| 
|-
! Packet 25
| 25
| 8
| 
| 
|-
! Packet 26
| 26
| 16
| 
| 
|-
! Packet 27
| 27
| 3
| 
| 
|-
! Packet 28
| 28
| 7
| 
| 
|-
! Packet 29
| 29
| 3
| 
| 
|-
! Packet 30
| 30
| Variable (byte)
| 
| 
|-
! Packet 31
| 31
| Variable (byte)
| 
| 
|-
! Packet 32
| 32
| 4
| 
| 
|-
! Packet 33
| 33
| 0
| 
| 
|-
! Packet 34
| 34
| 6
| 
| 
|-
! Packet 35
| 35
| Variable (byte)
| 
| 
|-
! Packet 36
| 36
| 6
| 
| 
|-
! Packet 37
| 37
| 4
| 
| 
|-
! Packet 38
| 38
| 7
| 
| 
|-
! Packet 39
| 39
| 7
| 
| 
|-
! Packet 40
| 40
| 8
| 
| 
|-
! Packet 41
| 41
| 12
| 
| 
|-
! Packet 42
| 42
| 15
| 
| 
|-
! Packet 43
| 43
| 3
| 
| 
|-
! Packet 44
| 44
| 3
| 
| 
|-
! Packet 45
| 45
| 7
| 
| 
|-
! Packet 46
| 46
| Variable (byte)
| 
| 
|-
! Packet 47
| 47
| 3
| 
| 
|-
! Packet 48
| 48
| 8
| 
| 
|-
! Packet 49
| 49
| 7
| 
| 
|-
! Packet 50
| 50
| Variable (byte)
| 
| 
|-
! Packet 51
| 51
| 3
| 
| 
|-
! Packet 52
| 52
| 4
| 
| 
|-
! Packet 53
| 53
| 18
| 
| 
|-
! Packet 54
| 54
| 8
| 
| 
|-
! Packet 55
| 55
| Variable (byte)
| 
| 
|-
! Packet 56
| 56
| 5
| 
| 
|-
! Packet 57
| 57
| 11
| 
| 
|-
! Packet 58
| 58
| 7
| 
| 
|-
! Packet 59
| 59
| Variable (byte)
| 
| 
|-
! Packet 60
| 60
| 1
| 
| 
|-
! Packet 61
| 61
| 3
| 
| 
|-
! Packet 62
| 62
| Variable (byte)
| 
| 
|-
! Packet 63
| 63
| 4
| 
| 
|-
! Packet 64
| 64
| 0
| 
| 
|-
! Packet 65
| 65
| 11
| 
| 
|-
! Packet 66
| 66
| 8
| 
| 
|-
! Packet 67
| 67
| 2
| 
| 
|-
! Packet 68
| 68
| Variable (byte)
| 
| 
|-
! Packet 69
| 69
| 3
| 
| 
|-
! Packet 70
| 70
| 3
| 
| 
|-
! Packet 71
| 71
| 16
| 
| 
|-
! Packet 72
| 72
| 3
| 
| 
|-
! Packet 73
| 73
| 2
| 
| 
|-
! Packet 74
| 74
| Variable (byte)
| 
| 
|-
! Packet 75
| 75
| 7
| 
| 
|-
! Packet 76
| 76
| 4
| 
| 
|-
! Packet 77
| 77
| 2
| 
| 
|-
! Packet 78
| 78
| 3
| 
| 
|-
! Packet 79
| 79
| Variable (byte)
| 
| 
|-
! Packet 80
| 80
| Variable (byte)
| 
| 
|-
! Packet 81
| 81
| Variable (byte)
| 
| 
|-
! Packet 82
| 82
| Variable (byte)
| 
| 
|-
! Packet 83
| 83
| 3
| 
| 
|-
! Packet 84
| 84
| 8
| 
| 
|-
! Packet 85
| 85
| 8
| 
| 
|-
! Packet 86
| 86
| 7
| 
| 
|-
! Packet 87
| 87
| 0
| 
| 
|-
! Packet 88
| 88
| Variable (byte)
| 
| 
|-
! Packet 89
| 89
| Variable (byte)
| 
| 
|-
! Packet 90
| 90
| 3
| 
| 
|-
! Packet 91
| 91
| 3
| 
| 
|-
! Packet 92
| 92
| 4
| 
| 
|-
! Packet 93
| 93
| Variable (byte)
| 
| 
|-
|}

==== '''Server-to-Client''' ====
{| class="wikitable" style="text-align: center"
|-
! Name
! Opcode
! Length
! Fields
! Description
|-
! Packet 0
| 0
| 2
| 
| 
|-
! Packet 1
| 1
| 0
| 
| 
|-
! Packet 2
| 2
| Variable (byte)
| 
| 
|-
! Packet 3
| 3
| Variable (byte)
| 
| 
|-
! Packet 4
| 4
| 0
| 
| 
|-
! Packet 5
| 5
| Variable (short)
| 
| 
|-
! Packet 6
| 6
| Variable (short)
| 
| 
|-
! Packet 7
| 7
| 20
| 
| 
|-
! Packet 8
| 8
| 6
| 
| 
|-
! Packet 9
| 9
| 10
| 
| 
|-
! Packet 10
| 10
| 2
| 
| 
|-
! Packet 11
| 11
| Variable (short)
| 
| 
|-
! Packet 12
| 12
| 7
| 
| 
|-
! Packet 13
| 13
| Variable (short)
| 
| 
|-
! Packet 14
| 14
| 6
| 
| 
|-
! Packet 15
| 15
| Variable (byte)
| 
| 
|-
! Packet 16
| 16
| 2
| 
| 
|-
! Packet 17
| 17
| Variable (byte)
| 
| 
|-
! Packet 18
| 18
| 1
| 
| 
|-
! Packet 19
| 19
| Variable (short)
| 
| 
|-
! Packet 20
| 20
| 4
| 
| 
|-
! Packet 21
| 21
| 3
| 
| 
|-
! Packet 22
| 22
| 6
| 
| 
|-
! Packet 23
| 23
| Variable (short)
| 
| 
|-
! Packet 24
| 24
| 5
| 
| 
|-
! Packet 25
| 25
| 17
| 
| 
|-
! Packet 26
| 26
| 6
| 
| 
|-
! Packet 27
| 27
| 16
| 
| 
|-
! Packet 28
| 28
| 0
| 
| 
|-
! Packet 29
| 29
| 4
| 
| 
|-
! Packet 30
| 30
| 3
| 
| 
|-
! Packet 31
| 31
| 10
| 
| 
|-
! Packet 32
| 32
| Variable (short)
| 
| 
|-
! Packet 33
| 33
| 6
| 
| 
|-
! Packet 34
| 34
| 6
| 
| 
|-
! Packet 35
| 35
| 7
| 
| 
|-
! Packet 36
| 36
| Variable (byte)
| 
| 
|-
! Packet 37
| 37
| 6
| 
| 
|-
! Packet 38
| 38
| Variable (short)
| 
| 
|-
! Packet 39
| 39
| 6
| 
| 
|-
! Packet 40
| 40
| 9
| 
| 
|-
! Packet 41
| 41
| Variable (short)
| 
| 
|-
! Packet 42
| 42
| 12
| 
| 
|-
! Packet 43
| 43
| 2
| 
| 
|-
! Packet 44
| 44
| 1
| 
| 
|-
! Packet 45
| 45
| Variable (byte)
| 
| 
|-
! Packet 46
| 46
| 3
| 
| 
|-
! Packet 47
| 47
| 8
| 
| 
|-
! Packet 48
| 48
| 4
| 
| 
|-
! Packet 49
| 49
| 3
| 
| 
|-
! Packet 50
| 50
| Variable (byte)
| 
| 
|-
! Packet 51
| 51
| 4
| 
| 
|-
! Packet 52
| 52
| Variable (byte)
| 
| 
|-
! Packet 53
| 53
| 0
| 
| 
|-
! Packet 54
| 54
| Variable (byte)
| 
| 
|-
! Packet 55
| 55
| 3
| 
| 
|-
! Packet 56
| 56
| Variable (short)
| 
| 
|-
! Packet 57
| 57
| 8
| 
| 
|-
! Packet 58
| 58
| 2
| 
| 
|-
! Packet 59
| 59
| 0
| 
| 
|-
! Packet 60
| 60
| 4
| 
| 
|-
! Packet 61
| 61
| 6
| 
| 
|-
! Packet 62
| 62
| Variable (byte)
| 
| 
|-
! Packet 63
| 63
| Variable (byte)
| 
| 
|-
! Packet 64
| 64
| 10
| 
| 
|-
! Packet 65
| 65
| 3
| 
| 
|-
! Packet 66
| 66
| 4
| 
| 
|-
! Packet 67
| 67
| 4
| 
| 
|-
! Packet 68
| 68
| 0
| 
| 
|-
! Packet 69
| 69
| Variable (short)
| 
| 
|-
! Packet 70
| 70
| Variable (short)
| 
| 
|-
! Packet 71
| 71
| Variable (byte)
| 
| 
|-
! Packet 72
| 72
| 8
| 
| 
|-
! Packet 73
| 73
| 3
| 
| 
|-
! Packet 74
| 74
| 6
| 
| 
|-
! Packet 75
| 75
| 4
| 
| 
|-
! Packet 76
| 76
| 7
| 
| 
|-
! Packet 77
| 77
| 3
| 
| 
|-
! Packet 78
| 78
| 4
| 
| 
|-
! Packet 79
| 79
| 1
| 
| 
|-
! Packet 80
| 80
| 6
| 
| 
|-
! Packet 81
| 81
| 10
| 
| 
|-
! Packet 82
| 82
| Variable (short)
| 
| 
|-
! Packet 83
| 83
| 1
| 
| 
|-
! Packet 84
| 84
| Variable (short)
| 
| 
|-
! Packet 85
| 85
| 0
| 
| 
|-
! Packet 86
| 86
| Variable (short)
| 
| 
|-
! Packet 87
| 87
| 8
| 
| 
|-
! Packet 88
| 88
| Variable (byte)
| 
| 
|-
! Packet 89
| 89
| 8
| 
| 
|-
! Packet 90
| 90
| Variable (byte)
| 
| 
|-
! Packet 91
| 91
| 10
| 
| 
|-
! Packet 92
| 92
| 28
| 
| 
|-
! Packet 93
| 93
| 12
| 
| 
|-
! Packet 94
| 94
| 0
| 
| 
|-
! Packet 95
| 95
| Variable (short)
| 
| 
|-
! Packet 96
| 96
| Variable (byte)
| 
| 
|-
! Packet 97
| 97
| 8
| 
| 
|-
! Packet 98
| 98
| Variable (byte)
| 
| 
|-
! Packet 99
| 99
| Variable (short)
| 
| 
|-
! Packet 100
| 100
| 3
| 
| 
|-
! Packet 101
| 101
| 4
| 
| 
|-
! Packet 102
| 102
| 5
| 
| 
|-
! Packet 103
| 103
| 0
| 
| 
|-
! Packet 104
| 104
| 1
| 
| 
|-
! Packet 105
| 105
| 6
| 
| 
|-
! Packet 106
| 106
| Variable (byte)
| 
| 
|-
! Packet 107
| 107
| 5
| 
| 
|-
! Packet 108
| 108
| 9
| 
| 
|-
! Packet 109
| 109
| 6
| 
| 
|-
! Packet 110
| 110
| 2
| 
| 
|-
! Packet 111
| 111
| 3
| 
| 
|-
! Packet 112
| 112
| Variable (short)
| 
| 
|-
! Packet 113
| 113
| 1
| 
| 
|-
! Packet 114
| 114
| Variable (byte)
| 
| 
|-
! Packet 115
| 115
| 6
| 
| 
|-
! Packet 116
| 116
| 12
| 
| 
|-
! Packet 117
| 117
| Variable (byte)
| 
| 
|-
! Packet 118
| 118
| Variable (byte)
| 
| 
|-
! Packet 119
| 119
| 11
| 
| 
|-
! Packet 120
| 120
| 6
| 
| 
|-
! Packet 121
| 121
| 4
| 
| 
|-
! Packet 122
| 122
| Variable (short)
| 
| 
|-
! Packet 123
| 123
| 3
| 
| 
|-
! Packet 124
| 124
| 7
| 
| 
|-
! Packet 125
| 125
| 0
| 
| 
|-
! Packet 126
| 126
| 0
| 
| 
|-
! Packet 127
| 127
| Variable (byte)
| 
| 
|-
! Packet 128
| 128
| 0
| 
| 
|-
! Packet 129
| 129
| 2
| 
| 
|-
! Packet 130
| 130
| Variable (byte)
| 
| 
|-
! Packet 131
| 131
| 6
| 
| 
|-
! Packet 132
| 132
| 5
| 
| 
|-
! Packet 133
| 133
| 6
| 
| 
|-
! Packet 134
| 134
| Variable (short)
| 
| 
|-
! Packet 135
| 135
| 6
| 
| 
|-
! Packet 136
| 136
| 6
| 
| 
|-
! Packet 137
| 137
| 2
| 
| 
|-
! Packet 138
| 138
| Variable (short)
| 
| 
|-
! Packet 139
| 139
| 7
| 
| 
|-
! Packet 140
| 140
| 1
| 
| 
|-
! Packet 141
| 141
| Variable (short)
| 
| 
|-
! Packet 142
| 142
| 10
| 
| 
|-
! Packet 143
| 143
| 6
| 
| 
|-
! Packet 144
| 144
| Variable (byte)
| 
| 
|-
|}

== '''Update Protocol''' ==

This section documents the communication between the client and server over the connection used to stream resources.

=== '''Handshake Response''' ===

After receiving a handshake for the update protocol, the server responds with one of the following packets:

{| class="wikitable" style="text-align: center"
|-
! Name
! Id
! Fields
! Description
|-
! OK
| 0
| style="text-align: left" | 
* required_resource_sizes: int32[27]
| Indicates a successful connection.
|-
! OUT_OF_DATE
| 6
| None
| Indicates that the client is outdated.
|-
! SERVER_FULL
| 7
| None
| Indicates that the server is full at the moment.
|-
! IP_LIMIT
| 9
| None
| Indicates that the client is being rate limited.
|-
|}

=== '''Packets''' ===
This section documents the packets sent between the client and server over the update connection. 

==== '''Client-to-Server''' ====
All packets sent by the client are 4 bytes long. Each packet includes a 1-byte opcode and a 3-byte payload.

{| class="wikitable" style="text-align: center"
|-
! Name
! Opcode
! Fields
! Description
|-
! Prefetch Request
| 0
| style="text-align: left" |
* index: int8
* file: int16
| A passive request for a resource.
|-
! Urgent Request
| 1
| style="text-align: left" |
* index: int8
* file: int16
| An urgent request for a resource.
|-
! Client Logged In
| 2
| style="text-align: left" |
* padding: int24
| Indicates that the client has logged in. May be useful for adjusting response rate.
|-
! Client Logged Out
| 3
| style="text-align: left" |
* padding: int24
| Indicates that the client has logged out. May be useful for adjusting response rate.
|-
! Update XOR Code
| 4
| style="text-align: left" |
* xor_code: int8
* padding: int16
| Proposes a code to be used to encrypt all traffic. May be used to bypass firewalls or related software.
|-
! Connection Information
| 6
| style="text-align: left" |
* version: int24
| Sent after a connection is established. The ''version'' field always has the value 3.
|-
! Drop Request Queue
| 7
| style="text-align: left" |
* padding: int24
| Asks for currently pending requests to be dropped by the server. This packet is restricted to administrators by the client.
|-
|}

==== '''Server-to-Client''' ====
The server responds to the client's requests for particular resources by sending back the (possibly compressed) files. The data is in the following format:

{| class="wikitable" style="text-align: center"
|-
! Field
! Description
|-
| index: int8
| The resource's index.
|-
| file: int16
| The resource's file number.
|-
| compression_type: int8
| The compression type of the file. Can be 0 (uncompressed), 1 (compressed using BZIP2), or 2 (compressed using GZIP).
|-
| file_size: int32
| The (possibly compressed) size of the file.
|-
| uncompressed_size: int32
| The uncompressed size of the file. This is only present if the file is compressed (i.e. the ''compression_type'' field is set to 1 or 2).
|-
| data: int8[file_size]
| The (possibly compressed) file data.
|-
|}

Of particular note is that the response is grouped into 512-byte blocks. For every block after the first, the first byte of the block '''must''' be 0xff (decimal 255).

In addition, if the client has updated its XOR code to be nonzero, the server must XOR each byte of the response with the chosen code before it sends it to the client.