102 lines
3.5 KiB
Plaintext
102 lines
3.5 KiB
Plaintext
SCGI: A Simple Common Gateway Interface alternative
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Neil Schemenauer <nas@python.ca>
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2008-06-23
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1. Introduction
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The SCGI protocol is a replacement for the Common Gateway Interface
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(CGI) protocol. It is a standard for applications to interface with
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HTTP servers. It is similar to FastCGI but is designed to be easier
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to implement.
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In this document, a string of 8-bit bytes may be written in two
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different forms: as a series of hexadecimal numbers between angle
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brackets, or as a sequence of ASCII characters between double quotes.
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For example, <68 65 6c 6c 6f 20 77 6f 72 6c 64 21> is a string of
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length 12; it is the same as the string "hello world!". Note that
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these notations are part of this document, not part of the protocol.
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2. Protocol
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The client connects to a SCGI server over a reliable stream protocol
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allowing transmission of 8-bit bytes. The client begins by sending a
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request. See section 3 for the format of the request. When the SCGI
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server sees the end of the request it sends back a response and closes
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the connection. The format of the response is not specified by this
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protocol.
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3. Request Format
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A request consists of a number of headers and a body. The format of
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the headers is:
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headers ::= header*
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header ::= name NUL value NUL
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name ::= notnull+
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value ::= notnull*
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notnull ::= <01> | <02> | <03> | ... | <ff>
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NUL = <00>
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Duplicate names are not allowed in the headers. The first header
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must have the name "CONTENT_LENGTH" and a value that is a nonempty
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sequence of ASCII digits giving the of the body length in decimal.
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The "CONTENT_LENGTH" header must always be present, even if its
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value is "0". There must also always be a header with the name
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"SCGI" and a value of "1". In order to facilitate the transition
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from CGI, standard CGI environment variables should be provided as
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SCGI headers.
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The headers are sent encoded as a netstring. Netstring encoding is
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explained in section 4. The body is sent following the headers and
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its length is specified by the "CONTENT_LENGTH" header.
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4. Netstrings
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Any string of 8-bit bytes may be encoded as [len]":"[string]",". Here
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[string] is the string and [len] is a nonempty sequence of ASCII
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digits giving the length of [string] in decimal. The ASCII digits are
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<30> for 0, <31> for 1, and so on up through <39> for 9. Extra zeros
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at the front of [len] are prohibited: [len] begins with <30> exactly
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when [string] is empty.
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For example, the string "hello world!" is encoded as <31 32 3a 68 65
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6c 6c 6f 20 77 6f 72 6c 64 21 2c>, i.e., "12:hello world!,". The empty
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string is encoded as "0:,".
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[len]":"[string]"," is called a netstring. [string] is called the
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interpretation of the netstring.
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5. Example
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The web server (a SCGI client) opens a connection and sends the
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concatenation of the following strings:
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"70:"
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"CONTENT_LENGTH" <00> "27" <00>
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"SCGI" <00> "1" <00>
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"REQUEST_METHOD" <00> "POST" <00>
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"REQUEST_URI" <00> "/deepthought" <00>
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","
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"What is the answer to life?"
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The SCGI server sends the following response:
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"Status: 200 OK" <0d 0a>
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"Content-Type: text/plain" <0d 0a>
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"" <0d 0a>
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"42"
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The SCGI server closes the connection.
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6. Copyright
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This document has been placed in the public domain.
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/* vim: set ai tw=74 et sw=4 sts=4: */
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