diff --git a/lib/GergelyPolonkai/SmsSender/Sender.php b/lib/GergelyPolonkai/SmsSender/Sender.php
index 887e587..88d9b86 100644
--- a/lib/GergelyPolonkai/SmsSender/Sender.php
+++ b/lib/GergelyPolonkai/SmsSender/Sender.php
@@ -1,6 +1,202 @@
 <?php
 namespace GergelyPolonkai\SmsSender;
 
+use RuntimeException;
+
 class Sender
 {
+    /**
+     * The internal libCURL handle
+     *
+     * @var resource $curl_handle
+     */
+    private $curl_handle;
+
+    /**
+     * The Cookie Jar
+     *
+     * @var array $cookies
+     */
+    private $cookies;
+
+    /**
+     * The authentication token received from the server during login
+     *
+     * @var string $token
+     */
+    private $token;
+
+    /**
+     * Constructor
+     *
+     * @param string  $senderUrl
+     * @param string  $contentType
+     * @param string  $contentEncoding
+     * @param boolean $verifySsl
+     * @param boolean $verbose
+     */
+    public function __construct($senderUrl, $contentType = 'application/json', $contentEncoding = 'utf-8', $verifySsl = false, $verbose = false)
+    {
+        /*
+         * Set up internal variables
+         */
+        $this->cookies = array();
+        $this->token = null;
+
+        /*
+         * Set up the CURL handle based on configuration options
+         */
+        $this->curl_handle = curl_init();
+        curl_setopt($this->curl_handle, CURLOPT_SSL_VERIFYPEER, $verifySsl);
+        curl_setopt($this->curl_handle, CURLOPT_URL, $senderUrl);
+        curl_setopt($this->curl_handle, CURLOPT_HTTPHEADER, array(
+            'Content-Type: ' . $contentType,
+            'Content-Encoding: ' . $contentEncoding,
+        ));
+        curl_setopt($this->curl_handle, CURLOPT_VERBOSE, $verbose);
+        // TODO: Make this configurable
+        curl_setopt($this->curl_handle, CURLOPT_PROXY, false);
+
+        curl_setopt($this->curl_handle, CURLOPT_POST, true);
+        curl_setopt($this->curl_handle, CURLOPT_HEADER, true);
+        curl_setopt($this->curl_handle, CURLOPT_TRANSFERTEXT, false);
+        curl_setopt($this->curl_handle, CURLOPT_RETURNTRANSFER, true);
+
+    }
+
+    /**
+     * Set a cookie for the connection
+     *
+     * @param string $name  The name of the cookie
+     * @param string $value The value of the cookie
+     */
+    public function setCookie($name, $value)
+    {
+        if ($value === null) {
+            unset($this->cookies[$name]);
+        } else {
+            $this->cookies[$name] = $value;
+        }
+    }
+
+    /**
+     * Get the value of a cookie
+     *
+     * @param  string $name The name of the cookie to get
+     * @return string       The value of the cookie, or null if the cookie is
+     *                      not found
+     */
+    public function getCookie($name)
+    {
+        if (array_key_exists($name, $this->cookies)) {
+            return $this->cookies[$name];
+        }
+
+        return null;
+    }
+
+    /**
+     * Get all the cookies for CURLOPT_COOKIE
+     *
+     * @return string All the cookies in the form "name=value; name=value"
+     */
+    private function getCookies()
+    {
+        $ret = array();
+        foreach ($this->cookies as $name => $value) {
+            $ret[] = urlencode($name) . '=' . urlencode($value);
+        }
+
+        return implode(';', $ret);
+    }
+
+    /**
+     * Send a JSON-RPC request to the server, and returns the result
+     *
+     * @param  string $method   The RPC method name
+     * @param  array $data      The post data
+     * @return mixed            The JSON data returned by the server
+     * @throws RuntimeException Upon a HTTP (CURL) error
+     * @throws RuntimeException Upon an invalid HTTP response
+     * @throws RuntimeException Upon a JSON response containing an error
+     * @throws RuntimeException Upon an invalid JSON response
+     */
+    private function jsonRequest($method, $data)
+    {
+        // TODO: Use JMSSerializer maybe?
+        $postData = json_encode(array(
+            'jsonrpc' => '1.0',
+            'id' => $method . '-' . uniqid(),
+            'method' => $method,
+            'params' => $data,
+        ));
+        curl_setopt($this->curl_handle, CURLOPT_POSTFIELDS, $postData);
+        curl_setopt($this->curl_handle, CURLOPT_COOKIE, $this->getCookies());
+        $result = curl_exec($this->curl_handle);
+
+        if ($result === false) {
+            throw new RuntimeException('CURL error: ' . curl_error($this->curl_handle));
+        }
+
+        $info = curl_getinfo($this->curl_handle);
+        if ($info['http_code'] != 200) {
+            throw new RuntimeException('Bad status code received (' . $info['http_code'] . ')!');
+        }
+
+        $m = array();
+        if (!preg_match('/(.*?)\r\n\r\n(.*)/s', $result, $m)) {
+            throw new RuntimeException('Invalid HTTP response!');
+        }
+        list($all, $headers, $body) = $m;
+
+        $matches = array();
+        preg_match_all('/Set-Cookie: ([^=]+)=(.*);/U', $headers, $matches, PREG_SET_ORDER);
+        foreach ($matches as $match) {
+            $this->setCookie($match[1], $match[2]);
+        }
+
+        // TODO: use JMSSerializer maybe?
+        $resultObj = json_decode($body, true);
+        if (!is_array($resultObj)) {
+            throw new RuntimeException('Result is not a JSON response!');
+        } elseif (array_key_exists('error', $resultObj) && ($resultObj['error'] !== null)) {
+            throw new RuntimeException('Result has an error: ' . $resultObj['error']);
+        } elseif (!array_key_exists('result', $resultObj)) {
+            throw new RuntimeException('Result has no "result" field');
+        }
+
+        return $resultObj['result'];
+    }
+
+    public function login($username, $password)
+    {
+        try {
+            $this->token = $this->jsonRequest('login', array($username, $password));
+        } catch (RuntimeException $e) {
+            $this->token = null;
+        }
+        return ($this->token !== null);
+    }
+
+    public function sendMessage($recipient, $message, array $passwordLocations)
+    {
+        if ($this->token === null) {
+            return false;
+        }
+
+        if ($passwordLocations === null) {
+            $passwordLocations = array();
+        }
+
+        $this->jsonRequest('send', array($this->token, $recipient, $message, $passwordLocations));
+
+        return true;
+    }
+
+    public function logout()
+    {
+        $this->jsonRequest('logout', array($this->token));
+
+        return true;
+    }
 }