What is the maximum SMS message length when sent through the Clickatell API for English and Spanish messages?
Is there is a difference between English and Spanish message lengths, since Spanish may contain Unicode characters?
From the SMS wikipedia page:
Messages are sent with the MAP MO- and MT-ForwardSM operations, whose payload length is limited by the constraints of the signaling protocol to precisely 140 octets (140 octets = 140 * 8 bits = 1120 bits).
Depending on which alphabet the subscriber has configured in the handset, this leads to the maximum individual short message sizes of 160 7-bit characters, 140 8-bit characters, or 70 16-bit characters.
As for your other question:
Is there is a difference between English and Spanish message lengths, since Spanish may contain Unicode characters?
No, there is no difference, as both English and Spanish are completely covered in the 8-bit Latin 1 character set.
SMS allows for multiple SMS messages to be strung together (with the length of each reducing to allow for "joining" data). I have experience of sending messages of length of 612 characters (4 SMS messages) - there is a reduction of 7 characters per message segment. On the receiving system the parts may be received out of sequence, with the message only making sense once all parts have been received. The Clickatell API allows this, although their API guide at https://www.clickatell.com/downloads/http/Clickatell_HTTP.pdf recommends a practical maximum of 3 messages it allows up to 35 (see section 4.2.7). So (ignoring unicode for the moment) you can send a message of 35 * 153 = 5355 characters via the Clickatell API. If you are sending unicode characters (which the OP is not) the character count for a single message is 70, reduced by 7 characters for each segment in concatenated message or 63 * 35 = 2205 unicode characters.
SMS messages can contain data of 140 bytes. However, SMS data is sent as a bitstream. This means if you are sending 7 bit ASCII, you can send 160 characters.
Related
I've recently started writing an MQTT library for a microcontroller. I've been following the specification document. Section 2.2.3 explains how the remaining length field (part of the fixed header) encodes the number of bytes to follow in the rest of the packet.
It uses a slightly odd encoding scheme:
Byte 0 = a mod 128, a /= 128, if a > 0, set top bit and add byte 1
Byte 1 = a mod 128, a /= 128, if a > 0, set top bit... etc
This variable length encoding seems odd in this application. You could easily transmit the same number using fewer bytes, especially once you get into numbers that take 2-4 bytes using this scheme. MQTT was designed to be simple to use and implement. So why did they choose this scheme?
For example, decimal 15026222 would be encoded as 0xae 0x90 0x95 0x7, however in hexadecimal it's 0xE5482E -- 3 bytes instead of four. The overhead in calculating the encoding scheme and decoding it at the other end seems to contradict the idea that MQTT is supposed to be fast and simple to implement on an 8-bit microcontroller.
What are the benefits to this encoding scheme? Why is it used? The only blog post I could find that even mentions any motivation is this one, which says:
The encoding of the remaining length field requires a bit of additional bit and byte handling, but the benefit is that only a single byte is needed for most messages while preserving the capability to send larger message up to 268’435’455 bytes.
But that doesn't make sense to me. You could have even more messages be only a single byte if you used the entire first byte to represent 0-255 instead of 0-127. And if you used straight hexadecimal, you could represent a number as large as 4 294 967 295 instead of only 268 435 455.
Does anyone have any idea why this was used?
As the comment you cited explains, under the assumption that "only a single byte is needed for most messages", or in other words, under the assumption that most of the time a <= 127 only a single byte is needed to represent the value.
The alternatives are:
Use a value to explicitly indicate how many bytes (or bits) are needed for a. This would require dedicating at least 2 bits to support at most "4 byte" sized a for all messages.
Dedicate a fixed size for a, probably 4 bytes, for all messages. This is inferior if many (read: most) messages don't utilize this size and can't support larger values if that becomes a requirement.
I'm developing a system to integrate with an SMS API, and I was wondering whether or not newlines count towards the character limit, I can't find any documentation on this.
Thanks
Yes, it does. ANY character you embed in the message counts against the limit, whether it's "visible" or not. Even if it's not a printable character, you've still sent that character across the cell network and caused the cell network to use up (as they claim) vast amounts of bandwidth that much be charged ludicrous rates to handle.
Any character counts toward your SMS limit. Line breaks, included.
I actually can't find a standard or anything. But I do know the message size is limited to 160 7-bit characters, 140 8-bit characters, or 70 16-bit characters, depending on the alphabet used.
Sorry, I can't give you any sources.
I just tested it on my phone. Yes, a line break counts
Yes, each line break, space and carriage return adds to your character count.
1 space = 1 character
1 line break = 2 characters
Yes it does. also as a side note, i noticed that if there are any unicode characters in the text, the entire message is treated as unicode and the length of the message is multiplyed by three.
What is the maximum number of bytes for a single UTF-8 encoded character?
I'll be encrypting the bytes of a String encoded in UTF-8 and therefore need to be able to work out the maximum number of bytes for a UTF-8 encoded String.
Could someone confirm the maximum number of bytes for a single UTF-8 encoded character please
The maximum number of bytes per character is 4 according to RFC3629 which limited the character table to U+10FFFF:
In UTF-8, characters from the U+0000..U+10FFFF range (the UTF-16
accessible range) are encoded using sequences of 1 to 4 octets.
(The original specification allowed for up to six byte character codes for code points past U+10FFFF.)
Characters with a code less than 128 will require 1 byte only, and the next 1920 character codes require 2 bytes only. Unless you are working with an esoteric language, multiplying the character count by 4 will be a significant overestimation.
Without further context, I would say that the maximum number of bytes for a character in UTF-8 is
answer: 6 bytes
The author of the accepted answer correctly pointed this out as the "original specification". That was valid through RFC-2279 1. As J. Cocoe pointed out in the comments below, this changed in 2003 with RFC-3629 2, which limits UTF-8 to encoding for 21 bits, which can be handled with the encoding scheme using four bytes.
answer if covering all unicode: 4 bytes
But, in Java <= v7, they talk about a 3-byte maximum for representing unicode with UTF-8? That's because the original unicode specification only defined the basic multi-lingual plane (BMP), i.e. it is an older version of unicode, or subset of modern unicode. So
answer if representing only original unicode, the BMP: 3 bytes
But, the OP talks about going the other way. Not from characters to UTF-8 bytes, but from UTF-8 bytes to a "String" of bytes representation. Perhaps the author of the accepted answer got that from the context of the question, but this is not necessarily obvious, so may confuse the casual reader of this question.
Going from UTF-8 to native encoding, we have to look at how the "String" is implemented. Some languages, like Python >= 3 will represent each character with integer code points, which allows for 4 bytes per character = 32 bits to cover the 21 we need for unicode, with some waste. Why not exactly 21 bits? Because things are faster when they are byte-aligned. Some languages like Python <= 2 and Java represent characters using a UTF-16 encoding, which means that they have to use surrogate pairs to represent extended unicode (not BMP). Either way that's still 4 bytes maximum.
answer if going UTF-8 -> native encoding: 4 bytes
So, final conclusion, 4 is the most common right answer, so we got it right. But, mileage could vary.
The maximum number of bytes to support US-ASCII, a standard English alphabet encoding, is 1. But limiting text to English is becoming less desirable or practical as time goes by.
Unicode was designed to represent the glyphs of all human languages, as well as many kinds of symbols, with a variety of rendering characteristics. UTF-8 is an efficient encoding for Unicode, although still biased toward English. UTF-8 is self-synchronizing: character boundaries are easily identified by scanning for well-defined bit patterns in either direction.
While the maximum number of bytes per UTF-8 character is 3 for supporting just the 2-byte address space of Plane 0, the Basic Multilingual Plane (BMP), which can be accepted as minimal support in some applications, it is 4 for supporting all 17 current planes of Unicode (as of 2019). It should be noted that many popular "emoji" characters are likely to be located in Plane 16, which requires 4 bytes.
However, this is just for basic character glyphs. There are also various modifiers, such as making accents appear over the previous character, and it is also possible to link together an arbitrary number of code points to construct one complex "grapheme". In real world programming, therefore, the use or assumption of a fixed maximum number of bytes per character will likely eventually result in a problem for your application.
These considerations imply that UTF-8 character strings should not "expanded" into arrays of fixed length prior to processing, as has sometimes been done. Instead, programming should be done directly, using string functions specifically designed for UTF-8.
Condidering just technical limitations - it's possible to have up to 7 bytes following current UTF8 encoding scheme. According to it - if first byte is not self-sufficient ASCII character, than it should have pattern: 1(n)0X(7-n), where n is <= 7.
Also theoretically it could be 8 but then first byte would have no zero bit at all. While other aspects, like continuation byte differing from leading, are still there (allowing error detection), I heared, that byte 11111111 could be invalid, but I can't be sure about that.
Limitatation for max 4 bytes is most likely for compatibility with UTF-16, which I tend to consider a legacy, because the only quality where it excels, is processing speed, but only if string byte order matches (i.e. we read 0xFEFF in the BOM).
I'm writing a code for handling SMS PDUs based on all those ETSI GSM documentations. There is one thing I need to ask about. PDU contains a User Data Length field followed by User Data. According to GSM 03.40, the UDL field is the number of septets of user data when the uncompressed GSM default alphabet is used. However, it also says, that when the data is compressed, then the UDL is the number of octets of user data.
See the quotes:
If the TP User Data is coded using the
GSM 7 bit default alphabet, the TP
User Data Length field gives an
integer representation of the number
of septets within the TP User Data
field to follow.
[...]
If the TP User Data is coded using
compressed GSM 7 bit default alphabet
or compressed 8 bit data or compressed
UCS2 [24] data, the TP User Data
Length field gives an integer
representation of the number of octets
after compression within the TP User
Data field to follow.
The problem is that when the 7-bit data is compressed and the number of octets of the compressed user data is a multiple of 7, you don't know whether the last 7 bits in the last octet are fill bits or a real character. I.e. 7 octets may contain either 7 or 8 7-bit characters when compression is on. And when the UDL field is the number of octets, how can you know whether those 7 octets contain 7 or 8 characters?? If UDL contained the number of septets, everything would be clear, right? So have I misunderstood the documentation or does it really work this way?
Could anyone please explain me how it really works? Thanks in advance!
As you are already aware, creating an MMS message requires you to add a UDH before your text message. The UDH becomes part of your payload, thus reducing the number of characters you can send per segment.
As it has become part of your payload, it needs to confirm with your payloads data requirement - which is 7 bit. The UDH however, is 8 bit, which clearly complicates things.
Consider the UDH of the following as an example (It's a UDH for a concatenated message):
050003000302
05 is the length of the UDH (the 5 octets which follow)
00 is the IEI
03 is the IEDL (3 more octets)
00 is a reference (this number must be the same in each of your concatenated message UDH's)
03 is the maximum number of messages
02 is the current message number.
This is 6 octets in total - equating to 48 bits. This is all and well, but since the UDH is actually part of your SMS message, what you have to do is add more bits so that the actual message starts on a septet boundary. A septet boundary is every 7 bits, so in this case, we will have to add 1 more bit of data to make the UDH 49 bits, and then we can add our standard GSM-7 encoded characters.
You can read up more about this from Here
So, the thing is that I misunderstood the meaning of the compression bit in the Data Coding Scheme byte. I thought it referred to the 7-bit alphabet packing method (where at least one character is stored within one byte) but it refers to Huffman compression.
Therefore, the question above was kind of stupid. Sorry for that :-).
What is the maximum length of a valid email address? Is it defined by any standard?
An email address must not exceed 254 characters.
This was accepted by the IETF following submitted erratum. A full diagnosis of any given address is available online. The original version of RFC 3696 described 320 as the maximum length, but John Klensin subsequently accepted an incorrect value, since a Path is defined as
Path = "<" [ A-d-l ":" ] Mailbox ">"
So the Mailbox element (i.e., the email address) has angle brackets around it to form a Path, which a maximum length of 254 characters to restrict the Path length to 256 characters or fewer.
The maximum length specified in RFC 5321 states:
The maximum total length of a reverse-path or forward-path is 256 characters.
RFC 3696 was corrected here.
People should be aware of the errata against RFC 3696 in particular. Three of the canonical examples are in fact invalid addresses.
I've collated a couple hundred test addresses, which you can find at http://www.dominicsayers.com/isemail
320
And the segments look like this
{64}#{255}
64 + 1 + 255 = 320
You should also read this if you are validating emails: I Knew How To Validate An Email Address Until I Read The RFC
user
The maximum total length of a user name is 64 characters.
domain
Maximum of 255 characters in the domain part (the one after the “#”)
However, there is a restriction in RFC 2821 reading:
The maximum total length of a reverse-path or forward-path is 256
characters, including the punctuation and element separators”. Since
addresses that don’t fit in those fields are not normally useful, the
upper limit on address lengths should normally be considered to be
256, but a path is defined as: Path = “<” [ A-d-l “:” ] Mailbox “>”
The forward-path will contain at least a pair of angle brackets in
addition to the Mailbox, which limits the email address to 254
characters.
According to the below article:
https://www.rfc-editor.org/rfc/rfc3696 (Page 6, Section 3)
It's mentioned that:
"There is a length limit on
email addresses. That limit is a maximum of 64 characters (octets)
in the "local part" (before the "#") and a maximum of 255 characters
(octets) in the domain part (after the "#") for a total length of 320
characters. Systems that handle email should be prepared to process
addresses which are that long, even though they are rarely
encountered."
So, the maximum total length for an email address is 320 characters
("local part": 64 + "#": 1 + "domain part": 255 which sums to 320)
To help the confused rookies like me, the answer to "What is the maximum length of a valid email address?" is 254 characters.
If your application uses an email, just set your field to accept 254 characters or less and you are good to go.
You can run a bunch of tests on an email to see if it is valid here. http://isemail.info/
The RFC, or Request for Comments is a type of publication from the Internet Engineering Task Force (IETF) that defines 254 characters as the limit. Located here - https://www.rfc-editor.org/rfc/rfc5321#section-4.5.3
The other answers muddy the water a bit.
Simple answer: 254 total chars in our control for email
256 are for the ENTIRE email address, which includes implied "<" at the beginning, and ">" at the end. Therefore, 254 are left over for our use.
TLDR Answer
Given an email address like...
me#example.com
The length limits are as follows:
Entire Email Address (aka: "The Path"): i.e., me#example.com -- 256 characters maximum.
Local-Part: i.e., me -- 64 character maximum.
Domain: i.e., example.com -- 254 characters maximum.
Source — TLDR;
The RFC standards are constantly evolving, but if you want a 2009 IETF source in a single line:
...the upper limit on address lengths should normally be considered to be 256. (Source: RFC3696.)
Source — The History
SMTP originally defined what a path was in RFC821, published August 1982, which is an official Internet Standard (most RFC's are only proposals). To quote it...
...a reverse-path, specifies who the mail is from.
...a forward-path, which specifies who the mail is to.
RFC2821, published in April 2001, is the Obsoleted Standard that defined our present maximum values for local-parts, domains, and paths. A new Draft Standard, RFC5321, published in October 2008, keeps the same limits. In between these two dates, RFC3696 was published, on February 2004. It mistakenly cites the maximum email address limit as 320-characters, but this document is "Informational" only, and states: "This memo provides information for the Internet community. It does not specify an Internet standard of any kind." So, we can disregard it.
To quote RFC2821, the modern, accepted standard as confirmed in RFC5321...
4.5.3.1.1. Local-part
The maximum total length of a user name or other local-part is 64
characters.
4.5.3.1.2. Domain
The maximum total length of a domain name or number is 255 characters.
4.5.3.1.3. Path
The maximum total length of a reverse-path or forward-path is 256
characters (including the punctuation and element separators).
You'll notice that I indicate a domain maximum of 254 and the RFC indicates a domain maximum of 255. It's a matter of simple arithmetic. A 255-character domain, plus the "#" sign, is a 256-character path, which is the max path length. An empty or blank name is invalid, though, so the domain actually has a maximum of 254.
Sadly, all the other answers are wrong. Most of them cite RFC 2821 or newer, which does not even define e-mail addresses. What it does do is define paths. E-mail addresses are defined by RFC 2822 (or newer) and can be much longer. Examples of valid addresses that are not valid paths are:
(Firstname Lastname) user#domain
Firstname Lastname <user#domain>
Both of these are the same mailbox written differently. So if your goal is to store e-mail addresses in a database, a limit of 254, 256 or 320 octets might be too low, although in practise, this is rarely going to be a problem.