Increase server to client com message limit.

Long sscsm com messages are now split over multiple chat messages.

README.md

@@ -83,7 +83,8 @@ change in a future release.
  - `sscsm.com_send(player_or_name, channel, msg)`: Sends `msg`
     (a JSON-compatible object) to `player_or_name` on the SSCSM com channel
     `channel`. Channel names should be `modname` or `modname:name` to prevent
-    conflicts.
+    conflicts. *Although the limit for server-to-client messages is 128MB, I
+    strongly recommend not sending large messages when not necessary.*
  - `sscsm.com_send_all(channel, msg)`: Sends `msg` to all clients that are
     running SSCSMs.
  - `sscsm.register_on_com_receive(channel, function(name, msg))`: Registers a

init.lua

@@ -202,6 +202,7 @@ local function validate_channel(channel)
     end
 end
 
+local msgids = {}
 function sscsm.com_send(pname, channel, msg)
     if minetest.is_player(pname) then
         pname = pname:get_player_name()
@@ -212,8 +213,34 @@ function sscsm.com_send(pname, channel, msg)
     else
         msg = assert(minetest.write_json(msg))
     end
-    minetest.chat_send_player(pname, '\001SSCSM_COM\001' .. channel .. '\001'
-        .. msg)
+
+    -- Short messages can be sent all at once
+    local prefix = '\001SSCSM_COM\001' .. channel .. '\001'
+    if #msg < 65300 then
+        minetest.chat_send_player(pname, prefix .. msg)
+        return
+    end
+
+    -- You should never send messages over 128MB to clients
+    assert(#msg < 134217728)
+
+    -- Otherwise split the message into multiple chunks
+    prefix = prefix .. '\001'
+    local id = #msgids + 1
+    local i = 0
+    msgids[id] = true
+    local total_msgs = math.ceil(#msg / 65000)
+    repeat
+        i = i + 1
+        minetest.chat_send_player(pname, prefix .. id .. '\001' .. i ..
+            '\001' .. total_msgs .. '\001' .. msg:sub(1, 65000))
+        msg = msg:sub(65001)
+    until msg == ""
+
+    -- Allow the ID to be reused on the next globalstep.
+    minetest.after(0, function()
+        msgids[id] = nil
+    end)
 end
 
 local registered_on_receive = {}
@@ -272,7 +299,7 @@ function sscsm.com_send_all(channel, msg)
 end
 
 -- Testing
-minetest.after(1, function()
+minetest.after(0, function()
     -- Check if any other SSCSMs have been registered.
     local c = 0
     for k, v in pairs(sscsm.registered_csms) do

sscsm_init.lua

@@ -212,6 +212,30 @@ function sscsm.register_on_com_receive(channel, func)
     table.insert(registered_on_receive[channel], func)
 end
 
+-- Load split messages
+local incoming_messages = {}
+local function load_split_message(chan, msg)
+    print('Got split message chunk')
+    local id, i, l, pkt = msg:match('^\1([^\1]+)\1([^\1]+)\1([^\1]+)\1(.*)$')
+    id, i, l = tonumber(id), tonumber(i), tonumber(l)
+
+    if not incoming_messages[id] then
+        incoming_messages[id] = {}
+    end
+    local msgs = incoming_messages[id]
+    msgs[i] = pkt
+
+    -- Return true if all the messages have been received
+    if #msgs < l then return end
+    for i = 1, l do
+        if not msgs[i] then
+            return
+        end
+    end
+    incoming_messages[id] = nil
+    return table.concat(msgs, '')
+end
+
 -- Detect messages and handle them
 minetest.register_on_receiving_chat_message(function(message)
     local chan, msg = message:match('^\001SSCSM_COM\001([^\001]*)\001(.*)$')
@@ -222,7 +246,16 @@ minetest.register_on_receiving_chat_message(function(message)
     if not callbacks then return end
 
     -- Load the message
-    if msg:sub(1, 1) == '\002' then
+    local prefix = msg:sub(1, 1)
+    if prefix == '\001' then
+        msg = load_split_message(chan, msg)
+        if not msg then
+            return true
+        end
+        prefix = msg:sub(1, 1)
+    end
+
+    if prefix == '\002' then
         msg = msg:sub(2)
     else
         msg = minetest.parse_json(msg)
@@ -230,7 +263,10 @@ minetest.register_on_receiving_chat_message(function(message)
 
     -- Run callbacks
     for _, func in ipairs(callbacks) do
-        func(msg)
+        local ok, msg = pcall(func, msg)
+        if not ok then
+            minetest.log('error', '[SSCSM] ' .. tostring(msg))
+        end
     end
     return true
 end)

sscsm_testing.lua

@@ -89,6 +89,10 @@ sscsm.every(60, function(param1)
 end, 123)
 
 sscsm.register_on_com_receive('sscsm:testing', function(msg)
-    print('Got ' .. minetest.serialize(msg):sub(8) .. ' from the server')
-    sscsm.com_send('sscsm:testing', msg)
+    if #msg > 400 then
+        print('Got large message of length ' .. #msg .. ' from the server')
+    else
+        sscsm.com_send('sscsm:testing', msg)
+        print('Got ' .. minetest.serialize(msg):sub(8) .. ' from the server')
+    end
 end)