[GUIDE] OBEX Protocol for Samsung GSM devices specification

Author: Apriorit (Device Team)

Permanent link: www(dot)apriorit(dot)com/dev-blog/58-samsung-obex-specification

This article describes the protocol of data exchange that is the modification of the well-known OBEX protocol used in the GSM Samsung phones from the SHP family. The described modification of this protocol lets you write data to the phone and also get and save them.

Introduction

This article describes the protocol of data exchange that is the modification of the well-known OBEX protocol used in the GSM Samsung phones from the SHP family. The described modification of this protocol lets you write data to the phone and also get and save them.

Samsung Corporation made the new line of phones from SHP family and implemented the support of OBEX protocol in them that had not been used in the phones of this company before. Tries to use the common OBEX protocol did not succeed. This problem was solved by means of sniffing the Samsung PC Studio 3.0 utility. The obtained results are given in the main part of the article.
This article will be useful for those who develop utilities for writing/reading information from the phones. The described protocol modification will solve the problem of communicating with the device.
First we consider three main types of the protocol commands. Then we pay our attention to the sequence of the commands sent to connect with the device, read data and finish the session. Then I will give some examples for the main commands. At the end of the article some summary will be given.

Main protocol commands format

All protocol commands can be divided into 2 types:
1. AKN-packages. They are packages to confirm the data receiving and request the next part of the extended package.
2. Data packages. They are initialization, acquiring, closing etc. There can be Request and Answer packages.
AKN package is one block with 3 bytes length: 0x83 0x00 0x03.

Request package has the following structure:

Size (bytes) Meaning Description
1 Package ID 0x80 Select the answering device, obtain the properties and establish connection
0x81 Finish the connection session
0x82 Write an object
0x83 Read an object
0x84 Reserved
0х85 Select the default directory on the receiving side
0хFF Cancel current operation

2 Package size The size of the whole package (from the zero byte and to the end)

… Data blocks Some number of data blocks that depends on the context of the command containing them.
Format:
Size (bytes) Meaning Description
1 Type Set the type of the data in the block
2 Size The size of the whole data block (from the zero byte and to the end)
N-3 Data Some data depending on the type specified by the first byte

The description of the Answer packages is given in the table below.

Size (bytes) Value Description
1 Package ID 0x90 Successful but not completed (received package is a part of the extended package)
0xA0 Successful and completed
0xC3 Access denied
0xC4 Not found
0xC9 Conflict
2 Package size The size of the whole package (from the zero byte and to the end)
… Data blocks Some number of data blocks that depends on the context of the command containing them.
Format:
Size (bytes) Meaning Description
1 Type Set the type of the data in the block
2 Size The size of the whole data block (from the zero byte and to the end)
N-3 Data Some data depending on the type specified by the first byte

The sequence of commands

As any standard communication protocol modified OBEX consists of the sequence of requests and answers. In general the communication session can be divided into 3 phases:
1. Initialization
2. Acquiring data
3. Closing the session

Table with the session description is given below.

Initialization phase

Request 41 54 2B 53 59 4E 43 4D 4C 3D 4D 4F 42 45 58 53 54 41 52 54 0D 0A AT+SYNCML=MOBEXS
Answer 41 54 2B 53 59 4E 43 4D 4C 3D 4D 4F 42 45 58 5354 41 52 54 0D 4F 4B 0D 0A AT+SYNCML=MOBEXSTART.OK..
Request 80 00 0F 11 00 FF FF 46 00 08 4D 4F 42 45 58 А.... F..MOBEX
Answer A0 00 14 12 00 05 78 CB 00 00 00 01 4A 00 08 4D 4F 42 45 58 а.....x╦....J..MOBEX

Acquiring phase

Request A series of requests and answers for acquiring data
Answer Note: if the first byte of the package is equal to 0x90 then it is so-called extended package and then the sending of AKN-package (0x83 0x00 0x03) is required,
after it the device will give us the other parts of the package.

Closing phase

Request 81 00 08 CB 00 00 00 01 Б..╦....
Answer A0 00 03 а..

Commands examples

Let’s consider some examples of the data acquisition. They will be the examples of working with the file system.

Obtaining the list of subfolders of the folder(m-obex/fs/folder_listing)

Request

83 00 29 CB 00 00 00 01 42 00 1C 6D 2D 6F 62 65 ?.)E....B..m-obex/fs/folder_listing..../.
78 2F 66 73 2F 66 6F 6C 64 65 72 5F 6C 69 73 74
69 6E 67 00 01 00 05 2F 00

Size (bytes) Value Description
1 0x83 Reading
2 0x00 0x29 Package size
1 0xCB Data block type
4 0x00 0x00 0x00 0x01 Reserved
1 0x42 Data block type (text)
2 0x00 0x1C Block size
N-3 m-obex/fs/folder_listing Block data (command name)
1 0x01 Block type (list)
2 0x00 0x05 Block size
N-3 0x2F 0x00 Block data
Note: “/” for the root, “/” for the other folders

Answer
A0 00 FC 42 00 1B 6D 2D 6F 62 65 78 2F 66 73 2F .uB..m-obex/fs/
66 6F 6C 64 65 72 5F 6C 69 73 74 69 6E 67 C3 00 folder_listingA.
00 00 D6 49 00 D9 41 75 64 69 6F 2C 30 2C 31 31 ..OI.UAudio,0,11
31 30 30 31 30 31 30 2C 32 30 30 34 3A 30 33 3A 1001010,2004:03:
30 31 20 30 31 3A 30 33 3A 30 30 5C 72 5C 6E 47 01 01:03:00\r\nG
72 61 70 68 69 63 73 2C 30 2C 31 31 31 30 30 31 raphics,0,111001
30 31 30 2C 32 30 30 34 3A 30 33 3A 30 31 20 30 010,2004:03:01 0
31 3A 30 33 3A 30 30 5C 72 5C 6E 56 69 64 65 6F 1:03:00\r\nVideo
2C 30 2C 31 31 31 30 30 31 30 31 30 2C 32 30 30 ,0,111001010,200
34 3A 30 33 3A 30 31 20 30 31 3A 30 33 3A 30 30 4:03:01 01:03:00
5C 72 5C 6E 4D 75 73 69 63 2C 30 2C 31 31 31 30 \r\nMusic,0,1110
30 31 30 31 30 2C 32 30 30 34 3A 30 33 3A 30 31 01010,2004:03:01
20 30 31 3A 30 33 3A 30 30 5C 72 5C 6E 4F 74 68 01:03:00\r\nOth
65 72 20 46 69 6C 65 73 2C 30 2C 31 er Files,0,1
31 31 30 30 31 30 31 30 2C 32 30 30 34 3A 30 33 11001010,2004:03
3A 30 31 20 30 31 3A 30 33 3A 30 30 5C 72 5C 6E :01 01:03:00\r\n

Size Value Description
1 0xA0 Successful operation
2 0x00 0x0F Package size
1 0x42 Block type
2 0x00 0x1C Block size
N-3 m-obex/fs/folder_listing(0x00) Block data
1 0xCB Block type
4 0x00 0x00 0x00 0xD6 Reserved
1 0x49 Block type
2 0x00 0xD9 Block size
N-3 Block data
Note: the list items are separated with the pair of symbols “\r\n”

Each element of the list is the folder description: [Name][Size(always 0)][Attributes][Modified][Created].

So in the example of these two commands you can see the general structure of the package in the modified OBEX protocol.

In conclusion I want to mention that the records in the phone book as well as the calendar are represented in VCard as it was in the previous versions of the OBEX protocols.