Overview

FIX Antenna (Java?)  products fully support UTF-8 encoding.

UTF-8 supports all the CJK (Chinese-Japanise-Korean) symbols but has no other meanings for 0x01 instead of SOH.

FIX-Protocol and non-ASCII characters

The support of non-ASCII characters was introduced in FIX-protocol since FIX 4.2 (??? https://www.fixtrading.org/standards/fix-4-2/).

The usage of the multibyte encodings is covered by FIX protocol with the followed algorithm:

1. Special Encoded fields are added for work with Non-ASCII symbols. 
2. The field MessageEncoding(347) should be specified with the encoding which are used in the other  Encoded* fields of the message.
3. The length fields (Encoded*Len) should contain the count of BYTES (Important: not count of symbols) contained in corresponding Encoded* field.

However, one can use UTF-8 in any text field. In order to keep FIX-protocol compatibility the counterparty must also expect UTF-8 encoding in the fields.

Work with Encoded fields

FIX Antenna and FIXEdge support and correctly processes Encoded fields and UTF-8 in non-encoded fields.

For FIX Antenna, it is user responsibility to convert ASCII string with UTF-8 content to the UTF-8 string and vice-versa.
The list of encoded tags

Example

The example shows how to work with tags: EncodedText (355) and EncodedTextLen (354) encoded by  MessageEncoding (347)

Message example: encoding testing.txt

For custom tags,

if the text tag has related pair tag with text length specified, the one can use UTF-8, Unicode or UTF-16 there, if the length should be specified in bytes. In case of the length should be specified in symbols, only UTF-8 can be used. In any scenario, counterparty should expect such encoding in such field.

FIX Protocol and UTF-16 Encoding

In UTF-16 or Unicode encodings, 0x01 is a page code and can be contained in the field content it makes UTF-16 incompatible with FIX-Protocol.

There is no need to use UTF-16 while it can be replaced with UTF-8