Original ipmsg protocol specification is written in Japanese.
This document was translated by Mr.Kanazawa.
This document is not verified yet.

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    IP Messenger communication protocol (Draft-9) 1996/02/21
                                Modified 2003/01/14

                                    H.Shirouzu
                              shirouzu@h.email.ne.jp
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About IP Messenger
    This is a Send/Receive message service using the TCP/UDP Port.

Characteristics
    IP Messenger can be installed in any OS if TCP/IP is used on your machine.
    Dynamic member recognition can be done within your network or specified network.
    You can exchange messages between all IPMsg members.

Function description
    Use TCP/UDP port(default:2425). See the following descriptions
    (Message Send/Receive: UDP, File Send/Receive: TCP)

1. Command

  1) Command functions (Low 8 bits from command number 32 bits)

    IPMSG_NOOPERATION No Operation
    IPMSG_BR_ENTRY Entry to service (Start-up with a Broadcast command)
    IPMSG_BR_EXIT Exit from service (End with a Broadcast command)
    IPMSG_ANSENTRY Notify a new entry
    IPMSG_BR_ABSENCE Change absence mode

    IPMSG_BR_ISGETLIST Search valid sending host members
    IPMSG_OKGETLIST Host list sending notice
    IPMSG_GETLIST Host list sending request
    IPMSG_ANSLIST Host list sending

    IPMSG_SENDMSG Message transmission
    IPMSG_RECVMSG Message receiving check

    IPMSG_READMSG Message open notice
    IPMSG_DELMSG Message discarded notice
    IPMSG_ANSREADMSG Message open confirmation notice(added from version-8 )

    IPMSG_GETFILEDATA File Transfer request by TCP
    IPMSG_RELEASEFILES Discard attachment file
    IPMSG_GETDIRFILES Attachment hierarchical file request

    IPMSG_GETINFO Get IPMSG version info.
    IPMSG_SENDINFO Send IPMSG version info.

    IPMSG_GETABSENCEINFO Get absence sentence
    IPMSG_SENDABSENCEINFO Send absence sentence

    IPMSG_GETPUBKEY RSA Public Key Acquisition
    IPMSG_ANSPUBKEY RSA Public Key Response

  2) Option flag (High 24 bits from command number 32 bits)

    IPMSG_ABSENCEOPT Absence mode(Member recognition command)
    IPMSG_SERVEROPT Server(Reserved)
    IPMSG_DIALUPOPT Send individual member recognition command

    IPMSG_SENDCHECKOPT Transmission check
    IPMSG_SECRETOPT Sealed message
    IPMSG_READCHECKOPT Sealed message check(added from ver8 )
    IPMSG_PASSWORDOPT Lock
    IPMSG_BROADCASTOPT Broadcast message
    IPMSG_MULTICASTOPT Multi-cast(Multiple casts selection)
    IPMSG_NEWMUTIOPT New version multi-cast(reserved)
    IPMSG_AUTORETOPT Automatic response(Ping-pong protection)
    IPMSG_NOLOGOPT No log files
    IPMSG_NOADDLISTOPT Notice to the members outside of BR_ENTRY

    IPMSG_FILEATTACHOPT File attachment
    IPMSG_ENCRYPTOPT Code

    IPMSG_NOPOPUPOPT (No longer valid)
    IPMSG_RETRYOPT Re-send flag(Use when acquiring HOSTLIST)

  3) Extended code flag (hex format combination)

    IPMSG_RSA_512
    IPMSG_RSA_1024
    IPMSG_RSA_2048
    IPMSG_RC2_40
    IPMSG_RC2_128
    IPMSG_RC2_256
    IPMSG_BLOWFISH_128
    IPMSG_BLOWFISH_256
    IPMSG_SIGN_MD5

  4) Extended files for attachment (fileattr low 8 bits)

    IPMSG_FILE_REGULAR
    IPMSG_FILE_DIR
    IPMSG_FILE_RETPARENT
    IPMSG_FILE_SYMLINK
    IPMSG_FILE_CDEV
    IPMSG_FILE_BDEV
    IPMSG_FILE_FIFO
    IPMSG_FILE_RESFORK

  5) Attachment file extended attribute(fileattr high 24 bits)

    IPMSG_FILE_RONLYOPT
    IPMSG_FILE_HIDDENOPT
    IPMSG_FILE_EXHIDDENOPT
    IPMSG_FILE_ARCHIVEOPT
    IPMSG_FILE_SYSTEMOPT

  6) Extended file attribute for attachment file

    IPMSG_FILE_UID
    IPMSG_FILE_USERNAME
    IPMSG_FILE_GID
    IPMSG_FILE_GROUPNAME
    IPMSG_FILE_PERM
    IPMSG_FILE_MAJORNO
    IPMSG_FILE_MINORNO
    IPMSG_FILE_CTIME
    IPMSG_FILE_MTIME
    IPMSG_FILE_ATIME
    IPMSG_FILE_CREATETIME

    IPMSG_FILE_CREATOR
    IPMSG_FILE_FILETYPE
    IPMSG_FILE_FINDERINFO

    IPMSG_FILE_ACL
    IPMSG_FILE_ALIASFNAME
    IPMSG_FILE_UNICODEFNAME


2.Command format(Use all character strings)

  1) Command(Format version-1)

    Ver(1) : PacketNo : SenderName : SenderHost : CommandNo : AdditionalSection

  2) An example for Message Send/Receive by using the current command format

    "1:100:shirouzu:jupiter:32:Hello"


3.Command process overview

  1) Member recognition

    An IPMSG_BR_ENTRY command notifies a new entry to the current
    members at start-up.

    All members add the new member to their list after getting a notification message.
    An IPMSG_ANSENTRY command sends a message back to the new member.

    The new member gets the current member data by a
    IPMSG_ANSENTRY command. All members can communicate as long as an
    IP packet exists.

    An IPMSG_BR_ABSENCE command broadcasts absence mode cancel or
    nickname change to all members. However, an IPMSG_ANSENTRY command
    does not send a message back, which is different from an IPMSG_BR_ENTRY
    command.

    IPMSG_BR_ENTRY, IPMSG_ANSENTRY, and IPMSG_BR_ABSENCE commands
    use an IPMSG_ABSENCEOPT flag for absence mode. Input a nickname to
    additional command.
    Add an IPMSG_DIALUPOPT flag for dial-up users who can't be reached by
    a broadcast command. A member recognition command needs to be
    sent individually to the members with this optional flag.

    (Extended group)IPMSG_BR_ENTRY and IPMSG_BR_ABSENCE commands
    sends a group name by adding the new group name after the current
    command format character strings (Input '\0' between the current
    command and extended name).

  2) Send/Receive Message
    Send Message uses an IPMSG_SENDMSG command that can input a message
    in the extended area.
    Receive Message sends back an IPMSG_RECVMSG command only
    if an IPMSG_SENDCHECKOPT flag is ON. Input the original packet number
    to the extended area.

    Broadcast Message Send uses an IPMSG_BOADCASTOPT command
    and an IPMSG_SENDMSG flag should be ON.
    Auto-Send packet(absence notice) needs to be added to IPMSG_AUTORETOPT
    for ping-pong protection. If either one or another packet is ON, then
    confirmation/auto-send packet is not sent back.

    Send Message Sealing needs to be an IPMSG_SECRETOPT packet ON.
    In this case, Receive Message sends an IPMSG_READMSG command.
    Input the original packet number to the extended area.

    (Additional IPMSG_NOADDLISTOPT)
    When receiving an IPMSG_SENDMSG packet from a host that is
    not on your Send/Receive list, IPMsg will either confirm a host by
    sending an IPMSG_BR_ENTRY command or add a host name to
    the Send/Receive list.
    However, single-shot Message Send/Receive action needs to be avoided.
    Add an IPMSG_NOADDLISTOPT flag to an IPMSG_SENDMSG command.

    (Additional IPMSG_READCHECKOPT from version-8 )
    When an IPMSG_READMSG command contains an IPMSG_READCHECKOPT flag,
    IPMsg process is the same as IPMSG_SENDMSG with an
    IPMSG_SENDCHECKOPT flag.
    However, Send Message uses an IPMSG_ANSREADMSG command,
    not IPMSG_RECVMSG.

  3) Message Send/Receive 亅encrypted extension (Added in the version-9 )

    Use the combination of Public-key(RSA) and common key(RC2/Blowfish).
    (Encrypted extension area is used in hex format.)

    (Public key acquisition)Send an IPMSG_GETPUBKEY command to Receive
    Message. Receive Message gets an IPMSG_ANSPUBKEY that
    means receiving RSA public key from Send Message.

    IPMSG_GETPUBKEY/IPMSG_ANSPUBKEY both require the value which is
    encryption capability (Exp. IPMSG_RSA_1024) flag uses "OR" at first
    part of extension

    In addition, In IPMSG_ANSPUBKEY, public key written as EE-NNNNNN
    E=Exponent丄N=method)devide by ':'. and Input the Fdelimiter '-'
    between E and N.

    This sequence can be skipped after the 2nd Send/Receive process by
    memorizing public key and encrypted data.
   
    (Encrypted message)After a sender creates a common key that is
    supported both sender and receiver, a common key can encrypt a message.
    In addition, a receiver's public key encrypts the common key.


    (Encrypted message transmission) IPMSG_ENCRYPTOPT is used in
    IPMSG_SENDMSG. At the first part of extension, input the value which
    is 'or' resoult from Convination of public key and common key type .
    Then use common key which encrypt with public key devide by ':'.
    Then input message which is eccrypted by public key devide by ':'.
    If both supports IPMSG_SIGN_XXX, then add ':' and signeture.

    Also, In the method of encode padding, PKCS#1ECB key is used for RSA,
    PKCS#5 CBC common key is used for RC2/blowfish.

    Also, The Packet related to Entry manifestation the capability of
    ecryption support using IPMSG_ENCRYPTOPT

  4) Extension with file attachment(Available from version-9 )

    An IPMSG_SENDMSG command with an IPMSG_FILEATTACHOPT flag for
    File transfer (download permission)notification sends a message
    with attachment.
    Input '\0' after the message and attachment file data.
   

    fileID:filename:size:mtime:fileattr[:extend-attr=val1
    [,val2...][:extend-attr2=...]]:\a:fileID...
    (size, mtime, and fileattr describe hex format.
      If a filename contains ':', please replace with "::".)

    When Receive Message downloads an attachment file, an IPMSG_GETFILEDATA
    command requests a data transmission packet to the TCP port that is the same number
    as the UDP sending port number. Input packetID:fileID: offset to the extended area.
    (Use all hex format.)
    File Transfer side receives the request. After recognizing that it's a correct request,
    then send the specified data (no format)

    When the data receiving side downloads a hierarchical attachment file,
    use an IPMSG_GETDIRFILES command and input a packetID:fileID
    to the extended area and send a data transmission request packet.
    (all hex format)

    Data sending side sends the following hierarchical data format.
    header-size:filename:file-size:fileattr[:extend-attr=val1
    [,val2...][:extend-attr2=...]]:contents-data
    Next headersize: Next filename...
    (All hex format except for filename and contetns-data)

    header-size is from the beginning of header-size to the delimiter ':'
    that is before contents-data. extend-attr can be omitted and used multiple
    extended attributes. Use '=' for data input.

    When fileattr is IPMSG_FILE_DIR, IPMsg recognizes that it is automatically
    in the directory, the next file data is after the directory.

    When fileattr is IPMSG_FILE_RETPARENT, IMPsg recognizes that it returns
    to the parent directory. In this case, File name is always "." and the attribute
    value is the current directory data.

    Sending process starts from the attachment directly and returns the
    IPMSG_FILE_RETPARENT command to the attachment directory.

    Add an IPMSG_FILEATTACHOPT flag for an Entry packet to support the
    attachment file.

  5) Other commands

    When acquiring different versions, send an IPMSG_GETINFO command.
    Receiving side sends the version information character string to
    extended area.

    Send an IPMSG_GETABSENCEINFO command for acquiring an absence message.
    Receiving side sends an IPMSG_SENDABSENCEINFO back if the status is absence mode.
    If the status is not absence mode, a character string "Not absence mode" will be sent back.

  6) Confirmation/Retry

    If a confirmation packet for IPMSG_SENDMSG or IPMSG_RECVMSG is not delivered
    within a specified time, then it will be sent again.
    A number of retry actions or interval period is depended on the current condition.


4. Other

  1) Linefeed

    Linefeed characters in Send Message is standardized with UNIX type ('0x0a').
    Please change if needed.

  2) Delimiter ':'

    ':' is used as a delimiter. You can't use this delimiter for user name
    and host name.
    If the use/host names contain a ':', please replace with another sign,
    for an example ';'.
    Although using this delimiter isn