To solve your problem, here is code you will need, please, do not just copy paste it, edit it so it will work for your SSM, especially AddChatCommand part.
You can just skip first 400 lines, it's just library for Lua, no changes needed there. Only the end of the code is important.
-- JSON library for Lua
json = loadstring([[--
-- json.lua
--
-- Copyright (c) 2019 rxi
--
-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-- of the Software, and to permit persons to whom the Software is furnished to do
-- so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.
--
local json = { _version = "0.1.2" }
-------------------------------------------------------------------------------
-- Encode
-------------------------------------------------------------------------------
local encode
local escape_char_map = {
  [ "\\" ] = "\\\\",
  [ "\"" ] = "\\\"",
  [ "\b" ] = "\\b",
  [ "\f" ] = "\\f",
  [ "\n" ] = "\\n",
  [ "\r" ] = "\\r",
  [ "\t" ] = "\\t",
}
local escape_char_map_inv = { [ "\\/" ] = "/" }
for k, v in pairs(escape_char_map) do
  escape_char_map_inv[v] = k
end
local function escape_char(c)
  return escape_char_map[c] or string.format("\\u%04x", c:byte())
end
local function encode_nil(val)
  return "null"
end
local function encode_table(val, stack)
  local res = {}
  stack = stack or {}
  -- Circular reference?
  if stack[val] then error("circular reference") end
  stack[val] = true
  if rawget(val, 1) ~= nil or next(val) == nil then
    -- Treat as array -- check keys are valid and it is not sparse
    local n = 0
    for k in pairs(val) do
      if type(k) ~= "number" then
        error("invalid table: mixed or invalid key types")
      end
      n = n + 1
    end
    if n ~= #val then
      error("invalid table: sparse array")
    end
    -- Encode
    for i, v in ipairs(val) do
      table.insert(res, encode(v, stack))
    end
    stack[val] = nil
    return "[" .. table.concat(res, ",") .. "]"
  else
    -- Treat as an object
    for k, v in pairs(val) do
      if type(k) ~= "string" then
        error("invalid table: mixed or invalid key types")
      end
      table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
    end
    stack[val] = nil
    return "{" .. table.concat(res, ",") .. "}"
  end
end
local function encode_string(val)
  return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
end
local function encode_number(val)
  -- Check for NaN, -inf and inf
  if val ~= val or val <= -math.huge or val >= math.huge then
    error("unexpected number value '" .. tostring(val) .. "'")
  end
  return string.format("%.14g", val)
end
local type_func_map = {
  [ "nil"     ] = encode_nil,
  [ "table"   ] = encode_table,
  [ "string"  ] = encode_string,
  [ "number"  ] = encode_number,
  [ "boolean" ] = tostring,
}
encode = function(val, stack)
  local t = type(val)
  local f = type_func_map[t]
  if f then
    return f(val, stack)
  end
  error("unexpected type '" .. t .. "'")
end
function json.encode(val)
  return ( encode(val) )
end
-------------------------------------------------------------------------------
-- Decode
-------------------------------------------------------------------------------
local parse
local function create_set(...)
  local res = {}
  for i = 1, select("#", ...) do
    res[ select(i, ...) ] = true
  end
  return res
end
local space_chars   = create_set(" ", "\t", "\r", "\n")
local delim_chars   = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
local escape_chars  = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
local literals      = create_set("true", "false", "null")
local literal_map = {
  [ "true"  ] = true,
  [ "false" ] = false,
  [ "null"  ] = nil,
}
local function next_char(str, idx, set, negate)
  for i = idx, #str do
    if set[str:sub(i, i)] ~= negate then
      return i
    end
  end
  return #str + 1
end
local function decode_error(str, idx, msg)
  local line_count = 1
  local col_count = 1
  for i = 1, idx - 1 do
    col_count = col_count + 1
    if str:sub(i, i) == "\n" then
      line_count = line_count + 1
      col_count = 1
    end
  end
  error( string.format("%s at line %d col %d", msg, line_count, col_count) )
end
local function codepoint_to_utf8(n)
  -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
  local f = math.floor
  if n <= 0x7f then
    return string.char(n)
  elseif n <= 0x7ff then
    return string.char(f(n / 64) + 192, n % 64 + 128)
  elseif n <= 0xffff then
    return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
  elseif n <= 0x10ffff then
    return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
                       f(n % 4096 / 64) + 128, n % 64 + 128)
  end
  error( string.format("invalid unicode codepoint '%x'", n) )
end
local function parse_unicode_escape(s)
  local n1 = tonumber( s:sub(3, 6),  16 )
  local n2 = tonumber( s:sub(9, 12), 16 )
  -- Surrogate pair?
  if n2 then
    return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
  else
    return codepoint_to_utf8(n1)
  end
end
local function parse_string(str, i)
  local has_unicode_escape = false
  local has_surrogate_escape = false
  local has_escape = false
  local last
  for j = i + 1, #str do
    local x = str:byte(j)
    if x < 32 then
      decode_error(str, j, "control character in string")
    end
    if last == 92 then -- "\\" (escape char)
      if x == 117 then -- "u" (unicode escape sequence)
        local hex = str:sub(j + 1, j + 5)
        if not hex:find("%x%x%x%x") then
          decode_error(str, j, "invalid unicode escape in string")
        end
        if hex:find("^[dD][89aAbB]") then
          has_surrogate_escape = true
        else
          has_unicode_escape = true
        end
      else
        local c = string.char(x)
        if not escape_chars[c] then
          decode_error(str, j, "invalid escape char '" .. c .. "' in string")
        end
        has_escape = true
      end
      last = nil
    elseif x == 34 then -- '"' (end of string)
      local s = str:sub(i + 1, j - 1)
      if has_surrogate_escape then
        s = s:gsub("\\u[dD][89aAbB]..\\u....", parse_unicode_escape)
      end
      if has_unicode_escape then
        s = s:gsub("\\u....", parse_unicode_escape)
      end
      if has_escape then
        s = s:gsub("\\.", escape_char_map_inv)
      end
      return s, j + 1
    else
      last = x
    end
  end
  decode_error(str, i, "expected closing quote for string")
end
local function parse_number(str, i)
  local x = next_char(str, i, delim_chars)
  local s = str:sub(i, x - 1)
  local n = tonumber(s)
  if not n then
    decode_error(str, i, "invalid number '" .. s .. "'")
  end
  return n, x
end
local function parse_literal(str, i)
  local x = next_char(str, i, delim_chars)
  local word = str:sub(i, x - 1)
  if not literals[word] then
    decode_error(str, i, "invalid literal '" .. word .. "'")
  end
  return literal_map[word], x
end
local function parse_array(str, i)
  local res = {}
  local n = 1
  i = i + 1
  while 1 do
    local x
    i = next_char(str, i, space_chars, true)
    -- Empty / end of array?
    if str:sub(i, i) == "]" then
      i = i + 1
      break
    end
    -- Read token
    x, i = parse(str, i)
    res[n] = x
    n = n + 1
    -- Next token
    i = next_char(str, i, space_chars, true)
    local chr = str:sub(i, i)
    i = i + 1
    if chr == "]" then break end
    if chr ~= "," then decode_error(str, i, "expected ']' or ','") end
  end
  return res, i
end
local function parse_object(str, i)
  local res = {}
  i = i + 1
  while 1 do
    local key, val
    i = next_char(str, i, space_chars, true)
    -- Empty / end of object?
    if str:sub(i, i) == "}" then
      i = i + 1
      break
    end
    -- Read key
    if str:sub(i, i) ~= '"' then
      decode_error(str, i, "expected string for key")
    end
    key, i = parse(str, i)
    -- Read ':' delimiter
    i = next_char(str, i, space_chars, true)
    if str:sub(i, i) ~= ":" then
      decode_error(str, i, "expected ':' after key")
    end
    i = next_char(str, i + 1, space_chars, true)
    -- Read value
    val, i = parse(str, i)
    -- Set
    res[key] = val
    -- Next token
    i = next_char(str, i, space_chars, true)
    local chr = str:sub(i, i)
    i = i + 1
    if chr == "}" then break end
    if chr ~= "," then decode_error(str, i, "expected '}' or ','") end
  end
  return res, i
end
local char_func_map = {
  [ '"' ] = parse_string,
  [ "0" ] = parse_number,
  [ "1" ] = parse_number,
  [ "2" ] = parse_number,
  [ "3" ] = parse_number,
  [ "4" ] = parse_number,
  [ "5" ] = parse_number,
  [ "6" ] = parse_number,
  [ "7" ] = parse_number,
  [ "8" ] = parse_number,
  [ "9" ] = parse_number,
  [ "-" ] = parse_number,
  [ "t" ] = parse_literal,
  [ "f" ] = parse_literal,
  [ "n" ] = parse_literal,
  [ "[" ] = parse_array,
  [ "{" ] = parse_object,
}
parse = function(str, idx)
  local chr = str:sub(idx, idx)
  local f = char_func_map[chr]
  if f then
    return f(str, idx)
  end
  decode_error(str, idx, "unexpected character '" .. chr .. "'")
end
function json.decode(str)
  if type(str) ~= "string" then
    error("expected argument of type string, got " .. type(str))
  end
  local res, idx = parse(str, next_char(str, 1, space_chars, true))
  idx = next_char(str, idx, space_chars, true)
  if idx <= #str then
    decode_error(str, idx, "trailing garbage")
  end
  return res
end
return json
]])()
-- Here real code begins
RPC = { ctr = 1; }
function RPC:CallOne(player, a, b, c)
	local payload = {}
	local channelId=player.actor:GetChannel();
	payload.id = self.ctr
	self.ctr = self.ctr + 1
	if type(b) == "string" then
		payload.class = a
		payload.method = b
		payload.params = c or {}
	else
		payload.method = a
		payload.params = b or {}
	end
	g_gameRules.onClient:ClStartWorking(channelId, player.id, "@" .. json.encode(payload))
	return { payload.id, player, false }
end
-- !!!EDIT THIS!!!
-- THIS COMMAND LOOKS AS FOLLOWS !rpc blablablablablablablablablablablablabla
-- so make sure that blablablablablablablablablablablablabla is in variable called "cmd" in order for this to work!!!
AddChatCommand("rpc", function(self, player, msg, cmd)
	if cmd then
		local obj = json.decode(cmd)
		if obj~=nil then
			if obj.id ~= nil then
				local params = obj.params;
				-- here you can use params.static_id to get player's "static ID" (100xxxx one)
				-- or params.uuid to get players hardware ID
				-- for example:
				if IsBannedProfileId(params.static_id) then BanPlayer(player) end
				players.profile = params.static_id
			end
		end
	end
end, {TEXT})
and when player connects, just do this:
RPC:CallOne(player, "UUID", { salt = "abcdefgh" })