{{refimprove, date=March 2019 External Machine Interface (EMI), an extension to Universal Computer Protocol (UCP), is a

protocol Protocol may refer to: Sociology and politics * Protocol (politics) Protocol originally (in Late Middle English, c. 15th century) meant the minutes or logbook taken at a meeting, upon which an agreement was based. The term now commonly refers to ...

primarily used to connect to

short message service centre Short may refer to: Places * Short (crater), a lunar impact crater on the near side of the Moon * Short, Mississippi, an unincorporated community * Short, Oklahoma, a census-designated place People * Short (surname) * List of people known ...

s (SMSCs) for

mobile telephone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This radio ...

s. The protocol was developed by CMG Wireless Data Solutions, now part of

Mavenir Mavenir Systems, Inc. is an American telecommunications software company, created in 2017 as a result of a three-way merger of existing companies and technologies, that develops and supplies Cloud native computing, cloud-native software to the ...

Syntax

A typical EMI/UCP exchange looks like this : ^B01/00045/O/30/66677789///1//////68656C6C6F/CE^C ^B01/00041/R/30/A//66677789:180594141236/F3^C The start of the

packet Packet may refer to: * A small container or pouch ** Packet (container), a small single use container ** Cigarette packet ** Sugar packet * Network packet, a formatted unit of data carried by a packet-mode computer network * Packet radio, a form ...

is signaled by ^B (STX, hex 02) and the end with ^C (ETX, hex 03). Fields within the packet are separated by / characters. The first four fields form the mandatory header. the third is the ''operation type'' (O for operation, R for result), and the fourth is the ''operation'' (here 30, "short message transfer"). The subsequent fields are dependent on the operation. In the first line above, '66677789' is the recipient's address (

telephone number A telephone number is the address of a Telecommunications, telecommunication endpoint, such as a telephone, in a telephone network, such as the public switched telephone network (PSTN). A telephone number typically consists of a Number, sequ ...

) and '68656C6C6F' is the content of the message, in this case the

ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...

string "hello". The second line is the response with a matching transaction reference number, where 'A' indicates that the message was successfully acknowledged by the SMSC, and a timestamp is suffixed to the phone number to show time of delivery. The final field is the

checksum A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify dat ...

, calculated simply by summing all bytes in the packet (including slashes) and taking the 8

least significant bit In computing, bit numbering is the convention used to identify the bit positions in a binary number. Bit significance and indexing In computing, the least significant bit (LSb) is the bit position in a binary integer representing the lowes ...

s from the result. The full specification is available on the LogicaCMG website developers' forum, but registration is required.

Technical limitations

The two-digit ''transaction reference number'' means that an entity sending text messages can only have 100 outstanding messages (per session); this can limit performance, but only over a slow network and with incorrectly configured applications on one's SMSC (for example one session, with number of windows greater than 100). In practice it does not have any impact on delivery throughput. The EMI UCP documentation does not specify a default alphabet for alphanumeric messages after decoding from hex digits. (It specifies an alphabet of IRA for the ''encoded'' message, which is the same as 7 bit

as 0-9 and A-Z are invariant characters). The related ETS 300 133-3 standard specifies the GSM-7 alphabet, which accommodates more languages than ASCII by replacing unprintable control codes with additional printable characters. In practice the GSM-7 alphabet is used. Other encodings, such as

UCS-2 UTF-16 (16-bit Unicode Transformation Format) is a character encoding that supports all 1,112,064 valid code points of Unicode. The encoding is variable-length as code points are encoded with one or two ''code units''. UTF-16 arose from an earli ...

, can be sent by using a transparent message and specifying the

Data Coding Scheme Data Coding Scheme is a one-Octet (computing), octet field in SMS, Short Messages (SM) and Cell Broadcast, Cell Broadcast Messages (CB) which carries a basic information how the recipient handset should process the received message. The information ...

Alternatives

Short message peer-to-peer protocol Short Message Peer-to-Peer (SMPP) in the telecommunications industry is an open, industry standard protocol designed to provide a flexible data communication interface for the transfer of short message data between External Short Messaging Enti ...

(SMPP) also provides

SMS Short Message Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile phones exchange short text messages, t ...

over TCP/ IP. * Computer Interface for Message Distribution (CIMD) developed by

Nokia Nokia Corporation is a Finnish multinational corporation, multinational telecommunications industry, telecommunications, technology company, information technology, and consumer electronics corporation, originally established as a pulp mill in 1 ...

Syntax

Technical limitations

Alternatives

External links