MessengerClient.lua

write("Initializing messenger...")
-- https://stackoverflow.com/a/7615129/13347795
function split(input, maxSplits, sep)
    if sep == nil then
        sep = ";"
    end
    splits = {}
    splitCount = 0
    for str in string.gmatch(input, "[^"..sep.."]+") do
        if maxSplits ~= nil and splitCount > maxSplits then
            splits[splitCount] = splits[splitCount]..sep..str
        else
            table.insert(splits, str)
            splitCount = splitCount + 1
        end
    end
    return splits
end
function readLoop()
    while true do
        message = read()
        rednet.broadcast(message, "broadcast-messenger-message")
   end
end
function rednetLoop()
    while true do
        id, message = rednet.receive("broadcast-messenger-message")
        print(id..": "..message)
   end
end
print(" Done!")

print("Loading messages...")

peripheral.find("modem", rednet.open)

rednet.broadcast(nil, "request-messenger-backlog")
_, response = rednet.receive("response-messenger-backlog")
term.clear()
term.setCursorPos(1, 1)

for _, row in ipairs(split(response, nil, "\n")) do
    date, time, id, message = table.unpack(split(row, 3))
    if message ~= nil then
        if id == tostring(os.getComputerID()) then
            print(message)
        else
            print(id..": "..message)
        end
    end
end

parallel.waitForAll(readLoop, rednetLoop)