private String escapeSockJsSpecialChars(char[] characters) {
        StringBuilder result = new StringBuilder();
        for (char c : characters) {
            if (isSockJsSpecialChar(c)) {
                result.append('\\').append('u');
                String hex = Integer.toHexString(c).toLowerCase();
                for (int i = 0; i < (4 - hex.length()); i++) {
                    result.append('0');
                }
                result.append(hex);
            } else {
                result.append(c);
            }
        }
        return result.toString();
    }
private String escapeSockJsSpecialChars ( char [ ] characters ) { StringBuilder result = new StringBuilder ( ) ; for ( char c : characters ) { if ( isSockJsSpecialChar ( c ) ) { result . append ( '\\' ) . append ( 'u' ) ; String hex = Integer . toHexString ( c ) . toLowerCase ( ) ; for ( int i = 0 ; i < ( 4 - hex . length ( ) ) ; i ++ ) { result . append ( '0' ) ; } result . append ( hex ) ; } else { result . append ( c ) ; } } return result . toString ( ) ; }
See "JSON Unicode Encoding" section of SockJS protocol.