RednetTerminal

local m = peripheral.find "modem"

local function prompt(what, default)
    write(what .. "> ")
    local result = read()
    if result == "" then
        print("Defaulted to", textutils.serialise(default))
        return default
    end
    return result
end

local protocol = prompt("Protocol", nil)
local sender = tonumber(prompt("Sender", os.getComputerID()))
local recipient = tonumber(prompt("Recipient", rednet.CHANNEL_BROADCAST))

m.open(rednet.CHANNEL_REPEAT)

local function send(from, protocol, content, to)
    local packet = {
        nMessageID = math.random( 1, 2147483647 ),
        nRecipient = to,
        message = content,
        sProtocol = protocol,
    }

    m.transmit(to, from, packet)
    m.transmit(rednet.CHANNEL_REPEAT, from, packet)
end

local function receive()
    local _, _, chan, replyChan, message = os.pullEvent "modem_message"
    return message.nRecipient, replyChan, message.message, message.sProtocol
end

local function recvLoop()
    while true do
        local recipient, sender, message, protocol = receive()
        local text = sender .. ">" .. recipient
        if protocol then text = text .. " (" .. protocol .. ")" end
        text = text .. " " .. textutils.serialise(message)
        print(text)
    end
end

local function sendLoop()
    while true do
        write "|> "
        local msg = read()
        send(sender, protocol, msg, recipient)
    end
end

parallel.waitForAll(sendLoop, recvLoop)