RAI - Request-Answer-Interface

rai is a node.js module to easily generate text based command line servers. When a client sends something to the server, the first word of the line is treated as a command and the rest of the line as binary payload.

Build Status

In addition to line based commands, there's also a data mode, to transmit everygting received. And there's also an option to switch to TLS mode for secure connections.

This way it is trivial to create SMTP, POP3 or similar servers.


npm install rai


Simple server

var RAIServer = require("rai").RAIServer;

// create a RAIServer on port 1234
var server = new RAIServer();

// Start listening for client connections
server.on("connect", function(client){

    // Greet the client

    // Wait for a command
    client.on("command", function(command, payload){

        if(command == "STATUS"){
            client.send("Status is OK!");
        }else if(command == "QUIT"){
            client.send("Unknown command");



Server only emits 'connect' and 'error' events, while the client objects emit 'timeout', 'error' and 'end' in addition to data related events.

Starting a server

Server can be started with new RAIServer([options]) where options is an optional parameters object with the following properties:

  • debug - if set to true print traffic to console
  • disconnectOnTimeout - if set to true close the connection on disconnect
  • secureConnection - if set to true close the connection on disconnect
  • credentials - credentials for secureConnection and STARTTLS
  • timeout - timeout in milliseconds for disconnecting the client, defaults to 0 (no timeout)

Once the server has been set up, it can start listening for client connections with server.listen(port[, hostname][, callback]). Callback function gets an error object as a parameter if the listening failed.

var server = new RAIServer();
server.listen(25); // start listening for port 25 on "localhost"

Closing server

Server can be closed with server.end([callback]) where callback is run when the server is finally closed.

Sending data

Data can be sent with client.send(data) where data is either a String or a Buffer. "\r\n" is automatically appended to the data.


Forcing connection close

Connections can be ended with client.end()

if(command == "QUIT"){
    client.send("Good bye!");

TLS mode

TLS can be switched on with client.startTLS([credentials][, callback]) and the status can be listened with 'tls' (emitted when secure connection is established)

credentials is an object with strings of pem encoded key, cert and optionally an array ca. If credentials is not supplied, an autogenerated value is used.

if(command == "STARTTLS"){

client.on("tls", function(){
    console.log("Switched to secure connection");

If callback is not set 'tls' will be emitted on connection upgrade.

Data mode

Data mode can be turned on with client.startDataMode([endSequence]) and incoming chunks can be received with 'data'. The end of data mode can be detected by 'ready'.

endSequence is a String for matching the end (entire line) of the data stream. By default it's "." which is suitable for SMTP and POP3.

if(command == "DATA"){
    client.send("End data with <CR><LF>.<CR><LF>");

client.on("data", function(chunk){
    console.log("Data from client:", chunk);

client.on("ready", function(){
    client.send("Data received");


There is a possibility to set up a mockup client which sends a batch of commands one by one to the server and returns the last response and an array of all responses(except the TLS negotiation).

var runClientMockup = require("rai").runClientMockup;

var cmds = ["EHLO FOOBAR", "STARTTLS", "QUIT"];
runClientMockup(25, "mail.hot.ee", cmds, function(lastResponse, allResponses){
    console.log("Final:", lastResponse.toString("utf-8").trim());
    console.log("All:", allResponses.map(function(e){
        return e.toString("utf-8").trim()
    }).join(', '));

runClientMockup has he following parameters in the following order:

  • port - Port number
  • host - Hostname to connect to
  • commands - Command list (an array) to be sent to server
  • callback - Callback function to run on completion
  • debug - if set to true log all input/output

Response from the callback function is a Buffer and contains the last data received from the server and an array of Buffers with all data received from the server.