<HTML> <HEAD> <TITLE>YOOHOO and YOOHOO/2U2.</TITLE> </HEAD> <!-- Background white, links blue (unvisited), navy (visited), red (active) --> <BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#000080" ALINK="#FF0000" > <PRE> Document: FTS-0006 Version: 002 Date: 30-Nov-1991 YOOHOO and YOOHOO/2U2 The netmail handshake used by Opus-CBCS and other intelligent Fidonet mail handling packages Vince Perriello FidoNet 1:2343/491 Status of this document: This FTS (FidoNet(r) Technical Standard) specifies an optional standard for the FidoNet community. Implementation of the protocols defined in this document is not mandatory, but all implementations of these protocols are expected to adhere to this standard. Distribution of this document is subject to the restrictions listed below. Fido and FidoNet are registered marks of Tom Jennings and Fido Software LEGAL STUFF ----------- The original protocol and documentation are by Wynn Wagner III. Updates have been made to this document by Vince Perriello, who also is responsible for most of the sample routine included with this document. They are released to the public for any use whatsoever as long as you don't modify any transmitted structure or try to make money hawking either the sample code or this document as if you owned them. If you choose to use the method or the sample routines, you do so entirely at your own risk. It is possible that the routines will cause physical damage to your equipment, an invasion of fire ants, the plague, or an extended visit from in-laws. If any of that stuff (or anything else) happens, you accept the consequences totally. CREDITS ------- Fido and Fidonet are registered trademarks of Tom Jennings and Fido Software. ARCmail was originated by System Enhancement Associates. The ZModem protocol was designed by Chuck Forsberg. The SEAlink / SEAlink Overdrive protocols are copyrighted by System Enhancment Associates. The TeLink protocol was designed and first implemented by Tom Jennings. The state charts in this document were done by Vince Perriello. Rick Huebner designed and implemented the basic WaZOO file request method. Update request functionality was added by Vince Perriello. Bob Hartman is responsible for the addition of Domain support. FTS-0001, describing the base FidoNet protocol, was created by Randy Bush. FTS-0007, describing enhancement to FTS-0001 using SEAlink and/or SEAlink Overdrive, was created by Phil Becker. YooHoo and YooHoo/2u2 Page 2 Overview UPFRONT ------- YOOHOO and YOOHOO/2U2 are the initial handshakes for the WaZOO e-mail protocol. They are designed to let two systems establish a common ground for a netmail session while making sure that non-WaZOO software doesn't get upset by material it can't understand. The YOOHOO procedure begins as a single byte (0xf1). If the system on the other end doesn't reply to that byte, no further YOOHOO or WaZOO transmissions are attempted. To a non-WaZOO netmail system, the YOOHOO byte will simply seem like a byte of debris. The calling system initiates the YOOHOO by sending the attention character. If the receiving system seems interested, the calling system sends a 128 byte packet containing such information as system and sysop names as well as a "capability mask." A 16-bit CRC protects the integrity of the 128-byte packet. In response, the receiving system prepares a 128 byte packet to send back. This is the YOOHOO/2U2 procedure. FEATURES -------- The features of YOOHOO and YOOHOO/2U2 include * non-interference with systems that don't understand the handshake * almost foolproof method for identifying a remote system and establishing a common ground for transmission * built-in room to expand the capabilities of WaZOO without having to resort to a kludge USAGE ----- A calling system simply uses a routine that transmits both YooHoo and TSYNC handshake initiating characters to the called system. If the called system responds with an XMODEM 'NAK', an FTS-0001 session will be initiated. If an 'ENQ' is received, the `YooHoo_Sender()' routine will be invoked to handle the session negotiation. A receiving system can call a routine like `YooHoo_Receiver()' if it detects the YOOHOO character, or just drop into the FTS-0001 logic if it sees a TSYNC. This simple method allows a mailer to take care of both the TSYNC and the YOOHOO handshakes. YooHoo and YooHoo/2u2 Page 3 WaZOO Protocols PROTOCOLS --------- Currently there are four WaZOO methods in use: 1. ZedZap ------ a Zmodem variant. The originator does a batch send then goes into a receive batch mode. The called system does receive then send. In the event of a file request (see description below) made by the called system, one more turnaround is made to service the request. * Unlike the "True" Zmodem protocol described by Chuck Forsberg, ZedZap routines must be able to handle a batch mode that has no actual files. In other words, it is possible for there to be a init sequence followed immediately by a ZFIN. * The maximum packet size is 8192. This is usually varied based on the baud rate. For example, at 2400 it might be 2048 bytes, then for 9600 baud and above the maximum of 8192 could apply. Note that THIS IS A SIGNIFICANT VARIATION FROM STRICT ZMODEM IMPLEMENTATION. (There's another WaZOO capability bit for those systems which can not handle this block size) * Netmail packets are transmitted as files with names in the form "12345678.PKT". Because of this, multiple packets may be sent in a single session. * If the calling system transmits a .REQ file for file requests, the receiving system can respond to it. See "WaZOO File Requests" (below) for information on the .REQ file. 2. ZedZip ------ This capability is identical to ZedZap, but does not use buffers greater than 1K in size (like "True" Zmodem). It is also permissible to send a "null" packet in a ZedZip session. This allows a system which must use a strict Zmodem implementation to participate in a WaZOO session using Zmodem. 3. DietIFNA -------- The session operates like FTS-0001/FTS-0007. The notable exceptions are as follows: * The same packet naming convention as ZedZap applies, allowing more than one packet to be transmitted in a single session. YooHoo and YooHoo/2u2 Page 4 WaZOO Protocols * Telink file transfers don't even attempt to exchange file names using modem7. The receiving system extracts the file name from the Telink or SEAlink header block. * If SEAlink is used, run-ahead (the number of blocks to slide) is based on the baud rate: BlocksToSlide = BaudRate / 400, up to a max of 24 blocks. * When there is nothing to send, a system should remain quiet. In other words, the end of a session can be determined by a timeout. * Under no circumstances should "BARK" file request logic be active during a DietIFNA session. File requests, if any, should be transmitted using a .REQ file. Many implementations of DietIfna have been accomplished by the mere exchange of packets, followed by straight FTS-0001/0007 code. This is incorrect but probably not easily remedied at this point. We have made an effort to document this change in "reality" in this revision of the document. 4. Janus ----- Janus is a full-duplex simultaneous bidirectional file transfer protocol. In other words, it can send and receive files at the same time. It's very loosely derived from ZModem and HDLC/X.25 protocol technology, in that it uses variable length data-typed packets, and that transmission of file data does not require ACKs. The protocol is documented elsewhere; it is beyond the scope of this document to do so. YooHoo and YooHoo/2u2 Page 5 Choosing WaZOO Methods How to decide which WaZOO method to use --------------------------------------- Since the called system has all the information necessary to decide what WaZOO method to employ, the best way to implement the process is for the calling system to send, in its capability mask, all the bits which correspond to methods it can use (or wants to use) in communicating with the called system. The called system then looks at these bits and sends back only the bit which corresponds to the method it wants to use. If the called system sends back a mask which contains more than one capability of the calling system, it can create a problem situation if one system arrives at its choice of methods differently from the other. Thus, when the called system doesn't make the choice, both systems should choose as follows: 1. Janus 2. ZedZap 3. ZedZip 4. DietIFNA The capability highest on the list which both systems indicate ability to execute should be the one employed. YooHoo and YooHoo/2u2 Page 6 WaZOO Filename conventions WaZOO FILENAMES --------------- 1. MESSAGE PACKETS ... xxxxxxxx.PKT Normal (unarchived) messages are sent in a file name that has a tag of .PKT. The "x" characters should be hex digits. 2. ARCmail ... xxxxxxxx.{MO|TU|WE|TH|FR|SA|SU}# Message packets are often shipped in an archive that has been compressed with some LZ utility. The file name consists of a name with hex digits. The tag is one of seven two-character prefixes ("MO", "TU", "WE", "TH", "FR", "SA" or "SU") and a number (0-9). This particular naming convention was established by ARCmail version 0.60, which is a defacto standard in FidoNet. 3. FILE REQUESTS ... xxxxxxxx.REQ This is explained below. In a nutshell, the file name consists of the receiving system's Fidonet address expressed as two 4-digit hex numbers. The file tag is .REQ. In a Janus session, the .REQ file isn't actually sent. Janus has a transaction system which sends the .REQ file one line at a time and then accepts the file(s) which the request generates. YooHoo and YooHoo/2u2 Page 7 Flow of a ZedZap or ZedZip Session FLOW OF A ZEDZAP OR ZEDZIP SESSION ---------------------------------- The calling system: * Send YooHoo * Receive YooHoo/2u2 * In a single batch, send bundles, files, file request (.REQ) files (in that order) * In a single batch, receive bundles, files, file requests, and requested files (in that order) * If a file request (.REQ) file came in, send all requested files in a single batch. Receiving system: * Receive YooHoo * Send YooHoo/2u2 * In a single batch, receive bundles, files, file requests * In a single batch, send bundles, files, our file requests, and respond to file requests that arrived from the remote system. * If we sent a .REQ file in the preceding step, receive all files in a single batch. YooHoo and YooHoo/2u2 Page 8 WaZOO File Requests WAZOO FILE REQUESTS ------------------- Rick Huebner, who adapted the ZModem routines for Opus, and the architect of the Janus file transfer protocol, designed the ".REQ file"-based file request system. REQ FILE: A WaZOO file request is based on a request file. The name of a request file is similar to the .OUT and .FLO files used by Opus-CBCS and similar mail products (such as BinkleyTerm). TEMPLATE: netnode.REQ EXAMPLE: 00010002.REQ ... a request being sent to 1/2 The .REQ file is simply a text file that contains the files we want from the remote system. Those file names can include wildcards, but should not contain a path. Optionally, there can be a password if the sending system requires one. The "netnode" part of the file name is built from the remote systems net and node numbers. Both numbers become 4-character hex numbers in the file name. Let's say we're requesting THIS.ARC and all node lists from 12/2. The file name would be 000C0002.REQ. The contents would look like this: this.arc nodelist.* If the sysop of 12/2 requires a password of THAT to get the file THIS.ARC, the REQ file contents would have to change: this.arc !that nodelist.* Transaction-level passwords (of 6 or fewer characters) follow the file name: <filename><single-space-character>!<password><cr> YooHoo and YooHoo/2u2 Page 9 WaZOO File Requests If the request is of the "update" genre, the type of update and the time, expressed as a UNIX-style long decimal ASCII number, follows the name, or in the event that there is a transaction-level password, the password. For example, an update request for file NEWOPUS.*, where you already have a file dated 1-January 1989, 00:00 and you live on the East Coast (GMT+06) would be: NEWOPUS.* +599634000 The sign is required, it indicates the type of update request. A '+' means that all files matching the filespec "NEWOPUS.*" newer than the shown time will be sent, a '-' means that all matching files with dates up to and including the indicated time will be sent. The complete format of an action line in an REQ file is, then: <filename>[<space>!<password>][<space><+/-><time>]<cr> MECHANISM: In a ZedZap or DietIfna session, the .REQ file is simply transmitted to the other system. It goes "as is" like any other file. In a Janus session, the .REQ file will be sent one line at a time and individually serviced by the other end. The other system can ignore the request, send some of the files, or send all of the files. There is no accounting or responsibilities on the part of the remote system. If your implementation is unable to process the update information for any reason, then you should process the line as a "regular" file request. NOTE: In the YooHoo packet, there's a bit that lets you know if the remote system currently accepts .REQ files. This will be a clue as to whether a .REQ file would be a waste of time or not. Procedurally, you just should not send a .REQ file to a system which indicates that it won't process it. YooHoo and YooHoo/2u2 Page 10 Structures and Definitions STRUCTURES AND DECLARATIONS --------------------------- #define ACK 0x06 #define NAK 0x15 #define ENQ 0x05 #define YOOHOO 0xf1 #define TSYNC 0xae struct _Hello { word signal; /* always 'o' (0x6f) */ word hello_version; /* currently 1 (0x01) */ word product; /* product code */ word product_maj; /* major revision of the product */ word product_min; /* minor revision of the product */ char my_name[60]; /* Other end's name, will include domain */ /* if DO_DOMAIN is set in capabilities mask*/ char sysop[20]; /* sysop's name */ word my_zone; /* 0== not supported */ word my_net; /* out primary net number */ word my_node; /* our primary node number */ word my_point; /* 0 == not supported */ byte my_password[8]; /* This is not necessarily null-terminated */ byte reserved2[8]; /* reserved by Opus */ word capabilities; /* see below */ byte reserved3[12]; /* for non-Opus systems with "approval" */ }; /* total size 128 bytes */ /*------------------------------------------------------------------------*/ /* YOOHOO<tm> CAPABILITY VALUES */ /*------------------------------------------------------------------------*/ #define Y_DIETIFNA 0x0001 /* Can do fast "FTS-0001" 0000 0000 0000 0001 */ #define FTB_USER 0x0002 /* Reserved by Opus-CBCS 0000 0000 0000 0010 */ #define ZED_ZIPPER 0x0004 /* Does ZModem, 1K blocks 0000 0000 0000 0100 */ #define ZED_ZAPPER 0x0008 /* Can do ZModem variant 0000 0000 0000 1000 */ #define DOES_IANUS 0x0010 /* Can do Janus 0000 0000 0001 0000 */ #define Bit_5 0x0020 /* reserved by FTSC 0000 0000 0010 0000 */ #define Bit_6 0x0040 /* reserved by FTSC 0000 0000 0100 0000 */ #define Bit_7 0x0080 /* reserved by FTSC 0000 0000 1000 0000 */ #define Bit_8 0x0100 /* reserved by FTSC 0000 0001 0000 0000 */ #define Bit_9 0x0200 /* reserved by FTSC 0000 0010 0000 0000 */ #define Bit_a 0x0400 /* reserved by FTSC 0000 0100 0000 0000 */ #define Bit_b 0x0800 /* reserved by FTSC 0000 1000 0000 0000 */ #define Bit_c 0x1000 /* reserved by FTSC 0001 0000 0000 0000 */ #define Bit_d 0x2000 /* reserved by FTSC 0010 0000 0000 0000 */ #define DO_DOMAIN 0x4000 /* Packet contains domain 0100 0000 0000 0000 */ #define WZ_FREQ 0x8000 /* WZ file req. ok 1000 0000 0000 0000 */ YooHoo and YooHoo/2u2 Page 11 Domain addressing in Hello Packet Since the invention of the WaZOO handshake, nearly every change in the FidoNet transport has been accessible by defining bits for new protocols, using the point number field in the structure, etc. With the advent of Domain addressing in FidoNet, this was no longer the case. There was no place set aside in the hello packet where domain info could be passed from one system to another. We have addressed this requirement by using some of the space set aside in the system name field for the domain. It is backward-compatible with all systems which determine the end of a string by use of a null. WaZOO systems that support domains communicate that fact by setting the DO_DOMAIN bit (hex 2000) in the capabilities mask. This tells the other side that they can expect to find a domain address in the packet. The domain name is stored at the end of the 'my_name' field. It is stored in its entirety (no abbreviations as in FSC-0045) after the system name. If the length of the system name plus the null terminator plus the length of the domain name plus terminator exceeds 60, the system name will be truncated (right to left) to make it fit. So, for a system named "FUBAR" at address 1:234/567@fidonet.org, the address and name fields in the header would look like this: hello.my_zone = 1 hello.my_net = 234 hello.my_node = 567 hello.my_point = 0 hello.my_name = 'F','U','B','A','R', 0, 'f','i','d','o','n','e','t', '.','o','r','g',0 hello.capabilities will contain the usual capabilities plus DO_DOMAIN. A remote system receiving this packet should look past the null in my_name to get the domain name. YooHoo and YooHoo/2u2 Page 12 Caller State Tables Calling System: The parts of FTS-0001 and FTS-0007 which deal with synchronization of calling and called system must be modified to deal with the reception and processing of the YooHoo character and exchange of Hello packets. The following state table may be used to initiate an FTS-0001 or a WaZOO session by the calling system. It replaces state S3 in the FTS-0001 table. .-----+----------+-------------------------+-------------------------+-----. |State| State | Predicate(s) | Action(s) | Next| | # | Name | | | Stat| |-----+----------+-------------------------+-------------------------+-----| | SS0 | SyncInit | | Prepare 3 sec Sync timer| | | | | | Prepare .5 sec NAK tmr | | | | | | Init NAK Count | | | | | | Start 60 sec master tmr | SS1 | |-----+----------+-------------------------+-------------------------+-----| | SS1 | SendSync | 1. Over 60 seconds | | | | | | or carrier lost | no response | exit| | | +-------------------------+-------------------------+-----| | | | 2. 3 sec elapsed | Clear Inbound buffer | | | | | or timer not started | Send YOOHOO, then TSYNC | | | | | | Start 3 sec Sync timer | SS2 | | | +-------------------------+-------------------------+-----| | | | 3. not elapsed | | SS2 | |-----+----------+-------------------------+-------------------------+-----| | SS2 | WaitResp | 1. Nothing received | require a response | SS1 | | | +-------------------------+-------------------------+-----| | | | 2. ENQ received | WaZOO Protocol selected | exit| | | +-------------------------+-------------------------+-----| | | | 3. 'C' received | probable FTS-0001 | SS3 | | | +-------------------------+-------------------------+-----| | | | 4. NAK received | probable FTS-0001 | SS3 | | | +-------------------------+-------------------------+-----| | | | 5. Debris (might include| Reset NAK timer | | | | | (YOOHOO|TSYNC) & 127)| if started | SS1 | |-----+----------+-------------------------+-------------------------+-----| | SS3 | NAKTmr | 1. Timer not expired | Zero NAK count | | | | | or timer not started | Start .5 sec NAK timer | SS1 | | | +-------------------------+-------------------------+-----| | | | 2. Timer expired | Bump NAK count | SS4 | |-----+----------+-------------------------+-------------------------+-----| | SS4 | NAKCount | 1. Count >= 2? | assume FTS-0001 | exit| | | +-------------------------+-------------------------+-----| | | | 2. Count < 2 | Keep looking | SS1 | `-----+----------+-------------------------+-------------------------+-----' YooHoo and YooHoo/2u2 Page 13 Caller State Tables Calling System (continued): The FTS-0001 exits from the above table should operate using the FTS-0001 state tables, starting at state S4. The "WaZOO detected" case should proceed using the following state table: .-----+----------+-------------------------+-------------------------+-----. |State| State | Predicate(s) | Action(s) | Next| | # | Name | | | Stat| |-----+----------+-------------------------+-------------------------+-----| | YS1 | SndHello | Successful | Looks like WaZOO | YS2 | | | (state +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | SH1) | Not successful | Repeat whole thing | exit| |-----+----------+-------------------------+-------------------------+-----| | YS2 | WaitResp | 30 sec timer expires | repeat whole thing | exit| | | | or lost carrier | | | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received YOOHOO | Another WaZOO, go | YS3 | | | | | process receive | | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received debris | Repeat whole thing | YS2 | |-----+----------+-------------------------+-------------------------+-----| | YS3 | GetHello | Information | Report Success | exit| | | (state | Successfully | | | | | RH1) | Exchanged | | | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Failure | Repeat whole thing | exit| `-----+----------+-------------------------+-------------------------+-----' The failure cases in this table may be retried. The retry should be from the point of synchronization. This means redoing the process in the SendSync table on Page 11. A really smart mailer could therefore do a YooHoo, exchange information, decide that it doesn't want to do WaZOO, fail out, and attempt an FTS-0001 session. If the packet exchange is successful, session method selection proceeds and then the chosen session method should be employed to exchange mail and files. YooHoo and YooHoo/2u2 Page 14 Called System State Tables The following state table may be used to initiate an FTS-0001 or a WaZOO session by the called system. It replaces states R1 and R2 in the FTS-0001 table. .-----+----------+-------------------------+-------------------------+-----. |State| State | Predicate(s) | Action(s) | Next| | # | Name | | | Stat| |-----+----------+-------------------------+-------------------------+-----| | RS0 | SyncInit | | Start 5 second idle tmr | RS1 | |-----+----------+-------------------------+-------------------------+-----| | RS1 | IdleWait | 1. 5 sec tmr expired | Take the initiative | RS2 | | | +-------------------------+-------------------------+-----| | | | 2. Carrier lost | Session aborted | exit| | | +-------------------------+-------------------------+-----| | | | 3. Peek = YOOHOO | Looks like a live WaZOO | RS3 | | | +-------------------------+-------------------------+-----| | | | 4. Peek = TSYNC | Live FTS-0001, we think | RS3 | | | +-------------------------+-------------------------+-----| | | | 5. Peek = CR, LF, space | He looks alive | RS2 | | | +-------------------------+-------------------------+-----| | | | 6. Other character | Eat it | RS1 | |-----+----------+-------------------------+-------------------------+-----| | RS2 |SendBanner| 1. Error returned | Session aborted | exit| | | +-------------------------+-------------------------+-----| | | | 2. Banner sent OK | | RS3 | |-----+----------+-------------------------+-------------------------+-----| | RS3 |RecvInit | | Start 20 sec timer | RS4 | | | | | Init 10 sec timer | | |-----+----------+-------------------------+-------------------------+-----| | RS4 |SendSync | 1. Error returned | Session aborted | exit| | |(xmit sync+-------------------------+-------------------------+-----| | |string) | 2. String sent OK | Watch for sender sync | RS5 | |-----+----------+-------------------------+-------------------------+-----| | RS5 | WaitSync | 1. Carrier lost | Session aborted | exit| | | +-------------------------+-------------------------+-----| | | | 2. YOOHOO received | WaZOO session selected | exit| | | +-------------------------+-------------------------+-----| | | | 3. TSYNC received | probable FTS-0001 | RS6 | | | +-------------------------+-------------------------+-----| | | | 4. CR received | Still sync'ing | RS4 | | | +-------------------------+-------------------------+-----| | | | 5. Other character rcvd | Get next input character| RS5 | | | +-------------------------+-------------------------+-----| | | | 6. 10 sec timer elapsed | FTS-0001 selected | exit| | | +-------------------------+-------------------------+-----| | | | 7. 20 sec timer elapsed | Not a mail session | exit| |-----+----------+-------------------------+-------------------------+-----| | RS6 | TsyncTmr | 1. Timer not running | Start 10 second timer | RS5 | | | | | Reset 20 sec timer | | | | +-------------------------+-------------------------+-----| | | | 2. Timer running | Two TSYNCS = FTS-0001 | exit| `-----+----------+-------------------------+-------------------------+-----' YooHoo and YooHoo/2u2 Page 15 Called System State Tables The FTS-0001 exits from the above table should operate using the FTS-0001 state tables, starting at state R3. The "WaZOO detected" case should proceed using the following state table: .-----+----------+-------------------------+-------------------------+-----. |State| State | Predicate(s) | Action(s) | Next| | # | Name | | | Stat| |-----+----------+-------------------------+-------------------------+-----| | YR1 | GetHello | Information | Start 20 sec timer | YR2 | | | (state | Successfully | Initialize retry count | | | | RH1) | Exchanged | Send YooHoo | | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Failure | Repeat whole thing | exit| |-----+----------+-------------------------+-------------------------+-----| | YR2 | WaitResp | 20 sec timeout | try again | YR3 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Lost carrier | Failure | exit| | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received ENQ | Go send hello | YR4 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received debris | Keep looking | YR2 | |-----+----------+-------------------------+-------------------------+-----| | YR3 | PollPeer | More than 3 retries | Give it up | exit| | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Less than 3 retries | Bump retry count | YR2 | | | | | Clear input buffer | | | | | | Send YOOHOO | | | | | | Restart 20 sec timer | | |-----+----------+-------------------------+-------------------------+-----| | YR4 | SndHello | Successful | All done, report success| exit| | | (state +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | SH1) | Not successful | Repeat whole thing | exit| `-----+----------+-------------------------+-------------------------+-----' The failure cases in states YR1, YR3 and YR4 of this table may be retried. The retry should be from the point of synchronization. This means redoing the process in the RecvSync table on Page 13, beginning at state RS3. A really smart mailer could therefore do a YooHoo, exchange information, decide that it doesn't want to (or cannot) do a WaZOO session, fail out, and attempt an FTS-0001 session. If the packet exchange is successful, session method selection proceeds and then the chosen session method should be employed to exchange mail and files. YooHoo and YooHoo/2u2 Page 16 Packet Exchange State Tables The following state table describes the transmission of the "Hello" packet from one system to its partner: .-----+----------+-------------------------+-------------------------+-----. |State| State | Predicate(s) | Action(s) | Next| | # | Name | | | Stat| |-----+----------+-------------------------+-------------------------+-----| | SH1 | InitSend | | Disable XON/XOFF | SH2 | | | | | Set retry count to 0 | | |-----+----------+-------------------------+-------------------------+-----| | SH2 | SendHedr | | Send Hex 1f, then | SH3 | | | | | Send HELLO struct | | |-----+----------+-------------------------+-------------------------+-----| | SH3 | SendCRC | | Clear Input Buffer | SH4 | | | | | Send two-byte CRC of pkt| | | | | | MSB followed by LSB | | | | | | Start 40 second timer | | |-----+----------+-------------------------+-------------------------+-----| | SH4 | GetResp | 40 second timer expires | Failed to send packet | exit| | | | or carrier lost | | | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | ACK received | Successful transmission | exit| | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | '?' received | Error, try retransmit | SH2 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | ENQ received | Out of sync? | SH2 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | other character recvd | Debris, keep watching | SH4 | `-----+----------+-------------------------+-------------------------+-----' YooHoo and YooHoo/2u2 Page 17 Packet Exchange State Tables The following state table describes the reception of the "Hello" packet sent to a system by its partner: .-----+----------+-------------------------+-------------------------+-----. |State| State | Predicate(s) | Action(s) | Next| | # | Name | | | Stat| |-----+----------+-------------------------+-------------------------+-----| | RH1 | SendENQ | | Start 2 minute timer | RH2 | | | | | Send an ENQ character | | |-----+----------+-------------------------+-------------------------+-----| | RH2 | WaitHedr | 2 minute timer expires | Report failure | exit| | | | or carrier lost | | | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received Hex 1f | Got header, get packet | RH5 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received other char | Debris, throw away | RH3 | | | | | Start 10 sec timer | | |-----+----------+-------------------------+-------------------------+-----| | RH3 | TossJunk | 10 sec timer expires | Too much noise | RH4 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Received Hex 1f | Got header, get packet | RH5 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Input buffer empty | Try to resynch | RH4 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Carrier lost | Report failure | exit| |-----+----------+-------------------------+-------------------------+-----| | RH4 | ReSynch | | Clear input buffer | RH2 | | | | | Send ENQ | | |-----+----------+-------------------------+-------------------------+-----| | RH5 | HdrSetup | | Initialize CRC | | | | | | Set 30 second timer | RH6 | |-----+----------+-------------------------+-------------------------+-----| | RH6 | GetHChar | 30 sec timer expires or | | | | | | carrier lost | Report failure | exit| | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | Character received | Process character | RH7 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | 10 seconds with no char | Error, try resync | RH9 | |-----+----------+-------------------------+-------------------------+-----| | RH7 | StoHChar | Buffer and CRC filled | Compare CRC | RH8 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | More characters needed | Reset 30 sec timer | RH6 | |-----+----------+-------------------------+-------------------------+-----| | RH8 | CheckCRC | CRC matches | Finish Receive | RH10| | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | CRC doesn't match | Handle error | RH9 | |-----+----------+-------------------------+-------------------------+-----| | RH9 | CountERR | Less than 10 errors | Send '?' (0x3f) | RH2 | | | +- - - - - - - - - - - - -+- - - - - - - - - - - - -+- - -| | | | 10 errors | Hang up, report failure | exit| |-----+----------+-------------------------+-------------------------+-----| | RH10| HelloOK | | Clear inbound buffer | exit| | | | | Send ACK | | `-----+----------+-------------------------+-------------------------+-----' </PRE> <A HREF="index.htm"><IMG SRC="../images/b_arrow.gif" ALT="Back" Border="0" width="33" height="35"> Go Back</A> </BODY> </HTML>