SOE Protocol Breakdown

SOE's Protocol is a systematic way to enhance the UDP protocol to make it more reliable, and also save bandwidth by merging and grouping packets. It can be combined in various ways, or not be used at all.

The format of the SOE Protocol varies depending on what type of operation it is. SOE Protocol can function as a stand alone packet, or as a Header to SWG Packets. What is true about all of the SOE Protocol is that the beginning contains 2 bytes known as the SOE Opcode. Majority also contain a footer. Assume all packets have footers unless otherwise mentioned. The table of opcodes are as follows:

Note- An SOE Opcode is stored as an unsigned short (uint16), and is in net byte order.

SOE OpCodes

(SOE Opcode)"in hex" (Meaning) (ENUM_NAME)"used in code" 00 01 Session Request (SOE_SESSION_REQUEST) 00 02 Session Response (SOE_SESSION_REPLY) 00 03 Multiple SOE Protocols (SOE_MULTI_SOE) 00 04 Not Used (SOE_NOT_USED) 00 05 Disconnect (SOE_DISCONNECT) 00 06 Keep Alive (SOE_PING) 00 07 Client Network Status Update (SOE_NET_STATUS_REQ) 00 08 Server Network Status Update (SOE_NET_STATUS_RES) 00 09 Channel 0 - Data Packet (SOE_CHL_DATA_A) 00 0A Channel 1 - Data Packet (SOE_CHL_DATA_B) 00 0B Channel 2 - Data Packet (SOE_CHL_DATA_C) 00 0C Channel 3 - Data Packet (SOE_CHL_DATA_D) 00 0D Channel 0 - Fragmented Data Packet (SOE_DATA_FRAG_A) 00 0E Channel 1 - Fragmented Data Packet (SOE_DATA_FRAG_B) 00 0F Channel 2 - Fragmented Data Packet (SOE_DATA_FRAG_C) 00 10 Channel 3 - Fragmented Data Packet (SOE_DATA_FRAG_D) 00 11 Channel 0 - Out of Order Packet (SOE_OUT_ORDER_PKT_A) 00 12 Channel 1 - Out of Order Packet (SOE_OUT_ORDER_PKT_B) 00 13 Channel 2 - Out of Order Packet (SOE_OUT_ORDER_PKT_C) 00 14 Channel 3 - Out of Order Packet (SOE_OUT_ORDER_PKT_D) 00 15 Channel 0 - Acknowledge Packet (SOE_ACK_A) 00 16 Channel 1 - Acknowledge Packet (SOE_ACK_B) 00 17 Channel 2 - Acknowledge Packet (SOE_ACK_C) 00 18 Channel 3 - Acknowledge Packet (SOE_ACK_D) 00 19 Channel 0 - Multi SWG Packets (SOE_MULTI_SWG_A) 00 1A Channel 1 - Multi SWG Packets (SOE_MULTI_SWG_B) 00 1B Channel 2 - Multi SWG Packets (SOE_MULTI_SWG_C) 00 1C Channel 3 - Multi SWG Packets (SOE_MULTI_SWG_D) 00 1D *Serious Error Acknowledge (SOE_FATAL_ERR) 00 1E *Serious Error Reply (SOE_FATAL_ERR_REP)

• Note: These functions are seen on very malformed packets. Very rare occurance and the client will usually disconnect. It's inclusion in the documentation is for completion ONLY. SWGEmu will disconnect automatically when reciving a Error Acknowledge, and it will NOT send any, rather just disconnect itself.

SOE has their protocol premade to allow various channels of data transmission. However, no game to this date utilizes the multiple channels. SWG will only be using channel 0 and it will be assumed throughout the rest of the packet documentation.

The following data is of packet breakdowns and explainations on each type. See the article "Packet Breakdown Format" for information on the specific used for documentation.

Packet Type -- 00 01

Packet Type 00 01

00 01 - Session Request (Client -> Server) SOE Opcode - Net Byte SHORT CRC Length - Net BYte INT Connection ID - Net Byte INT ClientUDPSize - Net Byte INT

The SOE Opcode is just the opcode number to identify the packet.

CRC Length is the amount of length of the CRC checksum to append at the end of a packet. SWG uses 2 bytes. Note CRC32 checksums are 32bit, making them 4 bytes, but only 2 are appended.

Connection ID is some type of identification used for the connection. Only other time seen is during a disconnect.

ClientUDPSize is the maximum size allocated for the client's UDP packet buffer. No packet is allowed to exceed this size. If it is larger, it must be fragmented. This size is equal to 496 bytes.

Note* This opcode DOES NOT have a footer.

Packet Type -- 00 02

Packet Type 00 02 - Session Response(Server -> Client)

SOE Opcode - Net Byte SHORT Connection ID - Net Byte SHORT CRCSeed - Net Byte INT CRCLength - BYTE UNKNOWN - SHORT ServerUDPSize - Net Byte INT

Connection ID is replied using the same ID sent by the Session Request. CRCSeed is a seed value used for the calculation of the CRC32 Checksum. CRCLength UNKNOWN is an unknown value that is constant and equal to 0x0104 (260). ServerUDPSize is the maximum size allocated for the server's UDP packet buffer. No packet is allowed to exceed this size.

So far the client has not sent anything large enough to fill this, or be fragmented. This size is equal to 496 bytes.

Note* This opcode DOES NOT have a footer.

Packet Type -- 00 03

Packet Type 00 03 - Multiple SOE Protocols(Various)

SOE Opcode - Net Byte SHORT Data Size - (VARIOUS) DATA - (VARIOUS) Data Size - (VARIOUS) DATA - (VARIOUS) ...

These packets allow the combination of 2 or more SOE Protocol packets or stand alone SWG Packets with SOE Protocol packets.

(SOE Protocol)((SOE Protocol)(SWG Packet)) or (SOE Protocol)(SWG Packet)

or as a better example:

(Multiple SOE Proto)(Ackowledge)(Data) or (Multiple SOE Proto)(Acknowledge)(SWG Packet) or (Multiple SOE Proto)(Acknowledge)(Acknowledge)

Each seperate packet is preceded by it's size. So a better example would be: (Multiple SOE Proto)(size1)(Acknowlede)(size2)(Data)

so a very basic hexadecimal version would be:

(00 03)  (04)  (00 15 00 00)  (0A)  (00 09 00 01 01 00 FF FF FF FF)
 multi   size   acknowledge   size              data

In the case where the size exceeds 0xFF (255) bytes, the following sytem is used for the "Data Size" component.

The first byte will be 0xFF. The next byte will be 0x01. The following byte will be how much to add to 255. Because no packet can exceed 496 bytes, The 3rd bye will never exceed 0xFF. We believe the 0x01 is the amount of following bytes to add to 255, but that cannot be determined.

(0XFF 0X01 0X01) = 255 + 1 = 256 bytes
(0xFF 0X01 0X0A) = 255 + 10 = 265 bytes
(0xFF 0x01 0x25) = 255 + 37 = 292 bytes

• NOTE: Because 255 may be done in a few ways, the following way is how we have seen it. (0xFF 0x00 0xFF) or 255 + 0 (do not add the following byte) = 255.

Packet Type -- 00 04

Packet Type 00 05 - Disconnect(VARIOUS)

SOE Opcode - Net Byte SHORT Connection ID - Net Byte INT Reason ID - Net Byte SHORT

Connection ID is the ID number assigned during the session request. Each client sends its own Connection ID. Reason ID is an ID number that corresponds for a reason for the disconnection.

This packet is sent whenever one side wants to disconnect. It resends the clients specific Connection ID established during the session handshake, and then a reason for disconnection. So far the standard reason ID seen has been 6. Others have been tested and do not have any different effect. No table correspnding IDs to reasons has been located.

Packet Type -- 00 06

00 06 - Keep Alive(VARIOUS)

SOE Opcode - Net Byte SHORT

This packet is simply a keep alive to tell the other side that is still connected, but idle. It only consists of the opcode and a footer.

Packet Type -- 00 07

00 07 - Client Network Status Update

SOE Opcode - Net Byte SHORT Data..

These packets consist of various data and network statistics. Because we do not care about network statistics, we will ignore these. To ignore these we send a special malformed Server Network Status Update.

Note: This packet is usually compressed but is optional.

Packet Type -- 00 08

00 08 - Server Network Status Update

SOE Opcode - Net Byte SHORT Data..

This packet is supposed to contain the Servers network statistics, however we felt it was a waste of time to reverse these as we do not care about the statistics. Instead we send 38 bytes of 0x00, and then compress the packet, but skip appending a CRC. The client seems to register that it recieved the servers statistics, but notices a bad CRC (or none in our case), and tosses out the packet as malformed. Because it recieved the packet it continues on without erroring.

Note: This packet is usually compressed but is optional.

Packet Type -- 00 09

00 09 - Channel 0 Data

SOE Opcode - Net Byte SHORT Sequence # - Net Byte SHORT SWG PACKET..

Sequence # is a sequence number applied to every data packet. It increments in order for each packet and is used to help determine out of order packets. This protocol is used to send an SWG Packet that NEEDS to be recieved by the other end. The reciver is then supposed to respond with a an ACKNOWLEDGE packet that contains the same sequence so the sender knows it has been recieved. This system ensures packets not only get sent correctly, but also stay in order.

After the sequence # comes the encapsulated SWG Packet.

Note* it is possible to combine multiple SWG PACKETs into a single 09. This is done similar to the 03 system with the sizes (1 byte, or the 0xFF 0x01 0xXX which is 255 + XX) but there are 2 bytes after the sequence that flag a multiple SWG packet. It looks something like this:

(00 09) (sequence) (00 19) (Size1) (SWG PACKET) (Size2) (SWG PACKET)
SOE op.  sequence   multi   size       data       size      data

Use these to combine SWG PACKETs together into 1 data packet/sequence number.

Packet Type -- 00 0D

00 0D - Fragmented Data Packet

SOE Opcode - Net Byte SHORT Sequence # - Net Byte SHORT *FragmentSize - Net Byte INT SWG Packet...

Sequence # is the same type of sequence number described in the "00 09 - Channel 0 Data" section. All the same rules apply.

• FragmentSize is the total size of the combined fragments. This only appears in the FIRST packet of a group of fragmented packets.

Next is just the piece data of the large SWG Packet. Fragments are made when the total UNCOMPRESSED packet exceeds the packet buffer size, which is 496 bytes.

Packet Type 00 11 - Out of Order Packet

SOE Opcode - Net Byte SHORT Sequence # - Net Byte SHORT

Sequence # is the sequence number of the out of order packet recieved. It will send one for every packet that is out of order, and the ones following.

So if packet sequences recieved are:

00 00
00 01

And then:

00 03

an out of order will be sent for the packet with sequence 00 03.

If the packet sequences recieved are:

00 00
00 01

And then:

00 03
00 04
00 05

An out of order packet will be sent for all 3 of the out of order sequences.

Packet Type -- 00 15

Packet Type 00 15 - Acknowledge

SOE Opcode - Net Byte SHORT Sequence # - Net Byte SHORT

Sequence # is the sequence number of the packet to acknowledge to the sender that it was recieved correctly. Every packet sent with a sequence number MUST be acknowledeged.

They do not neccesarily need to be Acknowledeged 1 by 1. For example: If packet sequences recieved are: 00 00 00 01 00 02

An Acknowledge of 00 15 00 02 will cover all the packets up to the sequence 00 02.

The client will stop processing packets after about 4 unacknowledeged packets so frequent acknowledges are needed.

Thanks to Acid1789 for the abundant information on the SOE Protocol!