'\" '\" Generated from file 'comm_wire\&.man' by tcllib/doctools with format 'nroff' '\" Copyright (c) 2005 Docs\&. Andreas Kupries '\" .TH "comm_wire" 3tcl 3 tcllib "Remote communication" .\" The -*- nroff -*- definitions below are for supplemental macros used .\" in Tcl/Tk manual entries. .\" .\" .AP type name in/out ?indent? .\" Start paragraph describing an argument to a library procedure. .\" type is type of argument (int, etc.), in/out is either "in", "out", .\" or "in/out" to describe whether procedure reads or modifies arg, .\" and indent is equivalent to second arg of .IP (shouldn't ever be .\" needed; use .AS below instead) .\" .\" .AS ?type? ?name? .\" Give maximum sizes of arguments for setting tab stops. Type and .\" name are examples of largest possible arguments that will be passed .\" to .AP later. If args are omitted, default tab stops are used. .\" .\" .BS .\" Start box enclosure. From here until next .BE, everything will be .\" enclosed in one large box. .\" .\" .BE .\" End of box enclosure. .\" .\" .CS .\" Begin code excerpt. .\" .\" .CE .\" End code excerpt. .\" .\" .VS ?version? ?br? .\" Begin vertical sidebar, for use in marking newly-changed parts .\" of man pages. The first argument is ignored and used for recording .\" the version when the .VS was added, so that the sidebars can be .\" found and removed when they reach a certain age. If another argument .\" is present, then a line break is forced before starting the sidebar. .\" .\" .VE .\" End of vertical sidebar. .\" .\" .DS .\" Begin an indented unfilled display. .\" .\" .DE .\" End of indented unfilled display. .\" .\" .SO ?manpage? .\" Start of list of standard options for a Tk widget. The manpage .\" argument defines where to look up the standard options; if .\" omitted, defaults to "options". The options follow on successive .\" lines, in three columns separated by tabs. .\" .\" .SE .\" End of list of standard options for a Tk widget. .\" .\" .OP cmdName dbName dbClass .\" Start of description of a specific option. cmdName gives the .\" option's name as specified in the class command, dbName gives .\" the option's name in the option database, and dbClass gives .\" the option's class in the option database. .\" .\" .UL arg1 arg2 .\" Print arg1 underlined, then print arg2 normally. .\" .\" .QW arg1 ?arg2? .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation). .\" .\" .PQ arg1 ?arg2? .\" Print an open parenthesis, arg1 in quotes, then arg2 normally .\" (for trailing punctuation) and then a closing parenthesis. .\" .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b .\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ta \\n()Au \\n()Bu .ie !"\\$3"" \{\ \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. .\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out .\" # BS - start boxed text .\" # ^y = starting y location .\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. .\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. .\" # VS - start vertical sidebar .\" # ^Y = starting y location .\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$2"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. .\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. .\" # Special macro to handle page bottom: finish off current .\" # box/sidebar if in box/sidebar mode, then invoked standard .\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. .\" # DS - begin display .de DS .RS .nf .sp .. .\" # DE - end display .de DE .fi .RE .sp .. .\" # SO - start of list of standard options .de SO 'ie '\\$1'' .ds So \\fBoptions\\fR 'el .ds So \\fB\\$1\\fR .SH "STANDARD OPTIONS" .LP .nf .ta 5.5c 11c .ft B .. .\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\*(So manual entry for details on the standard options. .. .\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. .\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. .\" # CE - end code excerpt .de CE .fi .RE .. .\" # UL - underline word .de UL \\$1\l'|0\(ul'\\$2 .. .\" # QW - apply quotation marks to word .de QW .ie '\\*(lq'"' ``\\$1''\\$2 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\$2 .. .\" # PQ - apply parens and quotation marks to word .de PQ .ie '\\*(lq'"' (``\\$1''\\$2)\\$3 .\"" fix emacs highlighting .el (\\*(lq\\$1\\*(rq\\$2)\\$3 .. .\" # QR - quoted range .de QR .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3 .. .\" # MT - "empty" string .de MT .QW "" .. .BS .SH NAME comm_wire \- The comm wire protocol .SH SYNOPSIS package require \fBcomm \fR .sp .BE .SH DESCRIPTION .PP The \fBcomm\fR command provides an inter-interpreter remote execution facility much like Tk's \fBsend(3tk)\fR, except that it uses sockets rather than the X server for the communication path\&. As a result, \fBcomm\fR works with multiple interpreters, works on Windows and Macintosh systems, and provides control over the remote execution path\&. .PP This document contains a specification of the various versions of the wire protocol used by comm internally for the communication between its endpoints\&. It has no relevance to users of \fBcomm\fR, only to developers who wish to modify the package, write a compatible facility in a different language, or some other facility based on the same protocol\&. .SH "WIRE PROTOCOL VERSION 3" .SS "BASIC LAYER" The basic encoding for \fIall\fR data is UTF-8\&. Because of this binary data, including the NULL character, can be sent over the wire as is, without the need for armoring it\&. .SS "BASIC MESSAGE LAYER" On top of the \fBBasic Layer\fR we have a \fImessage oriented\fR exchange of data\&. The totality of all characters written to the channel is a Tcl list, with each element a separate \fImessage\fR, each itself a list\&. The messages in the overall list are separated by EOL\&. Note that EOL characters can occur within the list as well\&. They can be distinguished from the message-separating EOL by the fact that the data from the beginning up to their location is not a valid Tcl list\&. .PP EOL is signaled through the linefeed character, i\&.e \fBLF\fR, or, hex \fB0x0a\fR\&. This is following the unix convention for line-endings\&. .PP As a list each message is composed of \fIwords\fR\&. Their meaning depends on when the message was sent in the overall exchange\&. This is described in the upcoming sections\&. .SS "NEGOTIATION MESSAGES - INITIAL HANDSHAKE" The command protocol is defined like this: .IP \(bu The first message send by a client to a server, when opening the connection, contains two words\&. The first word is a list as well, and contains the versions of the wire protocol the client is willing to accept, with the most preferred version first\&. The second word is the TCP port the client is listening on for connections to itself\&. The value \fB0\fR is used here to signal that the client will not listen for connections, i\&.e\&. that it is purely for sending commands, and not receiving them\&. .IP \(bu The first message sent by the server to the client, in response to the message above contains only one word\&. This word is a list, containing the string \fBvers\fR as its first element, and the version of the wire protocol the server has selected from the offered versions as the second\&. .PP .SS "SCRIPT/COMMAND MESSAGES" All messages coming after the \fBinitial handshake\fR consist of three words\&. These are an instruction, a transaction id, and the payload\&. The valid instructions are shown below\&. The transaction ids are used by the client to match any incoming replies to the command messages it sent\&. This means that a server has to copy the transaction id from a command message to the reply it sends for that message\&. .TP \fBsend\fR .TP \fBasync\fR .TP \fBcommand\fR The payload is the Tcl script to execute on the server\&. It is actually a list containing the script fragments\&. These fragment are \fBconcat\fRenated together by the server to form the full script to execute on the server side\&. This emulates the Tcl "eval" semantics\&. In most cases it is best to have only one word in the list, a list containing the exact command\&. .sp Examples: .sp .CS (a) {send 1 {{array get tcl_platform}}} (b) {send 1 {array get tcl_platform}} (c) {send 1 {array {get tcl_platform}}} are all valid representations of the same command\&. They are generated via (a') send {array get tcl_platform} (b') send array get tcl_platform (c') send array {get tcl_platform} respectively .CE .sp Note that (a), generated by (a'), is the usual form, if only single commands are sent by the client\&. For example constructed using \fBlist\fR, if the command contains variable arguments\&. Like .sp .CS send [list array get $the_variable] .CE .sp These three instructions all invoke the script on the server side\&. Their difference is in the treatment of result values, and thus determines if a reply is expected\&. .RS .TP \fBsend\fR A reply is expected\&. The sender is waiting for the result\&. .TP \fBasync\fR No reply is expected, the sender has no interest in the result and is not waiting for any\&. .TP \fBcommand\fR A reply is expected, but the sender is not waiting for it\&. It has arranged to get a process-internal notification when the result arrives\&. .RE .TP \fBreply\fR Like the previous three command, however the tcl script in the payload is highly restricted\&. It has to be a syntactically valid Tcl \fBreturn\fR command\&. This contains result code, value, error code, and error info\&. .sp Examples: .sp .CS {reply 1 {return -code 0 {}}} {reply 1 {return -code 0 {osVersion 2\&.4\&.21-99-default byteOrder littleEndian machine i686 platform unix os Linux user andreask wordSize 4}}} .CE .PP .SH "BUGS, IDEAS, FEEDBACK" This document, and the package it describes, will undoubtedly contain bugs and other problems\&. Please report such in the category \fIcomm\fR of the \fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&. Please also report any ideas for enhancements you may have for either package and/or documentation\&. .PP When proposing code changes, please provide \fIunified diffs\fR, i\&.e the output of \fBdiff -u\fR\&. .PP Note further that \fIattachments\fR are strongly preferred over inlined patches\&. Attachments can be made by going to the \fBEdit\fR form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar\&. .SH "SEE ALSO" comm .SH KEYWORDS comm, communication, ipc, message, remote communication, remote execution, rpc, socket .SH CATEGORY Programming tools .SH COPYRIGHT .nf Copyright (c) 2005 Docs\&. Andreas Kupries .fi