Trepia is a cool idea. It's an IM client that finds other people and sorts them by their proximity to you. But while it's a great idea, the client sucks, and it's not open source, so I can't fix its annoying problems myself. So, I decided to take some time to reverse engineer the protocol in hopes that somebody will write a better Trepia client. Maybe we'll be able to run it on *nix soon!

If you discover anything else, please post the additional information in a comment.

Prologue

I coded up a simple proxy server that would write out the packets as hex dumps, but most of that work turned out to be unnecessary, because Trepia actually uses uncompressed, unencrypted XML to communicate with the server. So I spent a bit of time reverse engineering the Trepia protocol. I've only put about 2 hours into it, but I'm hoping other people will take this information and run with it.

Overview

To create a new account in Trepia, the NEWACCT packet is used. After that, when you connect to Trepia, the client sends the CONNECT packet, to which the server replies with the LOGIN packet. From there, it's a loop that simply processes incoming packets. I believe it doesn't need to store any state about packets seen/expected for its basic operation. The exceptions are when logging in, creating a new account, or downloading the current user's profile.

Servers

The default trepia server is located at 207.44.192.59 and runs a Trepia server on ports 8201 through 8210.
[update] The server IP seems to have changed to 66.98.134.44.

Data Types

Trepia uses the following data types:

Type	Description	Example
Integer	An unbroken block of digits	1245
String	A block of text, encoded using XML entities. Line breaks, etc are also encoded as entities. Line breaks are encoded as a single 
	me & joe went to the store
it wasn't fun
MAC Address	A unique identifier for a network interface	00-50-BA-75-10-F7
Hex data	An unbroken string of lowercase hex characters	ee9356e428dd9507b32715da7235
Base64 data	A solid block of data encoded as base64	/9j/4AAQSkZJRgAQSkZJRgABAB==
Location	An integer that specifies a person's location. I've noticed that people close to me have closer numbers, so the distance between people may be simple subtraction operation between their locations. However, it doesn't sound like it would work, so I'm not sure about that. UNKNOWN FORMAT	1055792857

Packet format

Each packet is an XML block. The root tag specifies the packet type. Inside the root tag are immediate children, usually labeled 'a', 'b', 'c', 'd', etc. These children make up the parameters for the packet. So far, most children have been in a consistent order. However, the ones dealing with profiles or user data (ie DATAREPLY) have not always been in a consistent order. So, it's best not to rely on the order of the child nodes.

In the tables below, parameters are listed in the order the are generally sent/received by the official client.

Incoming Packets (packets from server to client)

Index: LOGIN | MEMBER | LOCATION | QUERY | DATAREPLY | NIX | PROFILE | RATED
Outgoing packets

Packet: LOGIN, Node: L, Parameters: 3
The LOGIN packet is sent in response to a CONNECT packet or a NEWACCT packet.

Parameter	Type	Meaning
a	Integer	Status: 0 - login successful, 1 - login incorrect, 2 - nickname taken (during registration), 4 - outdated client version?, OTHERS?
b	Location	Your current location
c	Integer	UNKNOWN, always 2 so far

<L>
  <a>0</a>
  <b>1055973014</b>
  <c>2</c>
</L>

Packet: MEMBER, Node: M, Parameters: 4
The MEMBER packet is sent to add/update users in the user list.

Parameter	Type	Meaning
a	Integer	User ID
b	Location	User's location
c	Integer	UNKNOWN, usually small numbers (1-4), but sometimes not. profile/update type? 1 - profile only?, 2/else - profile+picture?
d	Integer	UNKNOWN, can be empty?

<M>
  <a>12592</a>
  <b>1055792857</b>
  <c>2</c>
  <d>1738</d>
</M>

Packet: LOCATION, Node: R, Parameters: 2
The LOCATION packet is sent to update the location/insta-blog note for a user.

Parameter	Type	Meaning
a	Integer	User ID
b	String	User's location/note

<R>
  <a>1004</a>
  <b>Memory Leaks Fixed: NEW TREPIA</b>
</R>

Packet: QUERY, Node: Q, Parameters: 2
The QUERY packet is sent when a user sends a message to you.

Parameter	Type	Meaning
a	Integer	User ID
b	String	User's message

<Q>
  <a>12592</a>
  <b>test message</b>
</Q>

Packet: DATAREPLY, Node: O, Parameters: variable, 2+
The DATAREPLY packet is sent by the server in response to DATAREQ packets sent by the client.
Many of these fields can be missing or empty.

Parameter	Type	Meaning
a	Integer	User ID
b	Location	User's location
c	Integer	UNKNOWN, small numbers, always seems to accompany image data
d	String	User name
e	String	Email address
f	String	Homepage URL
g	String	First name
h	String	Last name
i	Integer (String?)	ICQ number
j	String	AIM ID
k	String	MSN ID
l	String	Yahoo ID
m	Integer	Age
n	String	Gender (M/F)
o	String	Profile text
p	String	Current location/insta-blog note?
q	Base64	Image file encoded as base64 - so far has been jpeg but may be other formats
r	String	Country
s	String	State/Province
t	String	City
u	String	Language(s)
v	String	School
w	String	Company
x	String	Location (dropdown box)

example 1 - profile

<O>
  <a>11263</a>
  <p>georgia</p>
  <b>1055298503</b>
  <d>USERNAME</d>
  <m>25</m>
  <n>M</n>
  <g>First</g>
  <h>Last</h>
  <o>Network &amp; Systems engineer (Cisco, Solaris, Linux, FreeBSD)</o>
  <e>spraycj@club2206.com</e>
  <i>164494238</i>
  <j>aaronkclark</j>
  <k>cryptojones@hotmail.com</k>
  <l>aaronkclark</l>
  <f>http://www.taoknights.org/aaronkclark</f>
  <r>United States</r>
  <s>TX</s>
  <t>San Antonio</t>
  <u>English</u>
  <v>School</v>
  <w>Company</w>
  <x>US -&gt; Georgia -&gt; Atlanta</x>
</O>

example 2 - photo data

<O>
  <a>7510</a>
  <c>1</c>
  <q>/9j/4AAQSkZJRgAB...kZJR</q>
</O>

Packet: NIX, Node: N, Parameters: 1
The NIX packet is sent by the server when a user has logged off.

Parameter	Type	Meaning
a	Integer	User ID

<N><a>5272</a></N>

Packet: PROFILE, Node: P, Parameters: 2
The PROFILE packet is sent by the server in response to the PROFREQ packet. The client can send an UPDPROF packet to alter the profile.

Parameter	Type	Meaning
a	Integer	User ID
b	String	User's password, sent as plaintext
c	String	Email address
d	String	Homepage URL
e	String	First name
f	String	Last name
g	Integer (String?)	ICQ number
h	String	AIM ID
i	String	MSN ID
j	String	Yahoo
k	Integer	Age
l	String	Gender (M/F)
m	String	Profile text
n	Base64	photo data - base64 encoded image file
o	String	Country
p	String	State/province
q	String	City
r	String	Language(s)
s	String	School
t	String	Company
u	String	Location (dropdown box)

<P>
  <a>Adam</a>
  <b>PASSWORD</b>
  <k>21</k>
  <l>M</l>
  <e>Adam</e>
  <f>M</f>
  <m>this is my profile</m>
  <c>adamm@san.rr.com</c>
  <g>27630686</g>
  <h></h>
  <i></i>
  <j></j>
  <d>http://www.adammil.net/</d>
  <o>USA</o>
  <p>CA</p>
  <q>San Diego</q>
  <r>English, Japanese</r>
  <s></s>
  <t></t>
  <u>US -&gt; California -&gt; San Diego</u>
  <n>/9j/4AAQ...qS5tz//Z</n>
</P>

Packet: RATED, Node: V, Parameters: 2
The RATED packet is sent when another user has rated you.

Parameter	Type	Meaning
a	Integer	User ID
b	Integer	Rating (1 - Cool, 2 - Interesting, etc)

<V><a>12592</a><b>1</V>

Outgoing Packets (packets from client to server)

Index: CONNECT | DATAREQ | MSG | PROFREQ | UPDPROF | UPDNOTE | RATEUSER | NEWACCT
Incoming packets

Packet: CONNECT, Node: C, Parameters: 5
The CONNECT packet is sent as soon as the client connects to the server. The server replies with the LOGIN packet.

Parameter	Type	Meaning
a	MAC Address	Your MAC address
b1	MAC Address	UNKNOWN, gateway MAC address???
c	String	Your User ID
d	Hex data	MD5 hash of the password
e	String	Client version

<C>
  <a>00-07-95-EA-E1-CE</a>
  <b1>00-50-BA-75-10-F7</b1>
  <c>AdamM</c>
  <d>bfad699370b9c64abd7ec844813fc4e1</d>
  <e>2.51</e>
</C>

Packet: DATAREQ, Node: D, Parameters: 2
The DATAREQ packet is sent by the client to request data about a particular user. The server will respond with corresponding DATAREPLY packets.

Parameter	Type	Meaning
a	Integer	User ID
b	Integer	Data requested, 1 - profile, 2 - photo, POSSIBLY OTHERS

<D>
  <a>7965</a>
  <b>1</b>
</D>

Packet: PROFREQ, Node: I, Parameters: 0
The PROFREQ packet is sent when the client wants to request its own profile. The server replies with a PROFILE packet.

<I></I>

Packet: MSG, Node: F, Parameters: 2
The MSG packet is sent by the client when the client wants to send a message to another user.

Parameter	Type	Meaning
a	Integer	User ID
b	String	Message to send to user

<F>
  <a>12592</a>
  <b>send message to pf</b>
</F>

Packet: UPDPROF, Node: K, Parameters: variable
The UPDPROF packet is sent when the client wants to update its profile.

The parameters consist of the items to change and the new values.

Parameter	Type	Meaning
a	String	User's password, sent as plaintext
b	String	Email address
c	String	Homepage URL
d	String	First name
e	String	Last name
f	Integer (String?)	ICQ number
g	String	AIM ID
h	String	MSN ID
i	String	Yahoo
j	Integer	Age
k	String	Gender (M/F)
l	String	Profile text
m	Base64	photo data - base64 encoded image file
n	String	Country
o	String	State/province
p	String	City
q	String	Language(s)
r	String	School
s	String	Company
t	String	Location (dropdown box)

<K>
  <a>password</a>
  <f>27630686</f>
  <m/>
  <t>US -&gt; California -&gt; San Jose</t>
</K>

Packet: UPDNOTE, Node: G, Parameters: 1
The UPDNOTE packet is sent when the client wants to update its location/insta-blog note.

Parameter	Type	Meaning
a	String	New note

<G><a>change my blog note</a></G>

Packet: RATEUSER, Node: U, Parameters: 2
The RATEUSER packet is sent when the client wants to rate another user.

Parameter	Type	Meaning
a	Integer	User ID
b	Integer	Rating (1 - Cool, 2 - Interesting, etc)

<U><a>12592</a><b>1</U>

Packet: NEWACCT, Node: J, Parameters: 14
The NEWACCT packet is sent to create a new Trepia account. The server will reply with a LOGIN packet.
Many of these fields may be empty, but I think none can be omitted.

Parameter	Type	Meaning
a	MAC Address	Your MAC address
b	MAC Address	UNKNOWN, gateway MAC address???
c	String	Client version
d	String	User name
e	String	Password in plain text
f	String	Email address
g	String	Homepage URL
h	String	First name
i	String	Last name
j	Integer	Age
k	String	Gender (M/F)
l	String	Profile text
m	Base64 data	Base64 encoded image file
n	String	Location (from dropdown box)

<J>
  <a>00-07-95-EA-E1-CE</a>
  <b1>00-50-BA-75-10-F7</b1>
  <c>2.51</c>
  <d>Adam</d>
  <e>password</e>
  <f>adamm@san.rr.com</f>
  <g>http://www.adammil.net/</g>
  <h>Adam</h>
  <i>Foo</i>
  <j>21</j>
  <k>M</k>
  <l>my profile</l>
  <m>/9j/4AAQ...+Jpgf//Z</m>
  <n>US -&gt; California -&gt; San Diego</n>
</J>