diff --git a/gatewayBackend.php b/gatewayBackend.php
index a74b319..e1b1a8b 100644
--- a/gatewayBackend.php
+++ b/gatewayBackend.php
@@ -23,22 +23,12 @@ interface gatewayBackend
         /**
          * removeToken() Remove a logged out user's token
          * 
+         * @param String $ip
+         * @param String $sessionId
          * @param String $token
          */
-        public function removeToken($token);
+        public function removeToken($ip, $sessionId, $token);
 
-	/**
-         * sendSMS()
-         * 
-         * Send SMS message to recipient's phone number
-	 * @param String $token
-         * @param String $recipient
-         * @param String $message
-         * @param Array $passwordLocations
-         * @return Boolean
-	 */
-	public function sendSMS($token, $recipient, $message, $passwordLocations);
-        
         /**
          * auditLog() Log audit messages
          * 
@@ -51,10 +41,11 @@ interface gatewayBackend
         /**
          * messageLog() Log sent messages
          * 
-         * @param String $recipient
-         * @param String $message
-         * @param String $ip
+         * @param Integer $senderId
+         * @param String  $recipient
+         * @param String  $message
+         * @param String  $ip
          */
-        public function messageLog($recipient, $message, $ip);
+        public function messageLog($senderId, $recipient, $message, $ip);
 }
 
diff --git a/gnokiiSMSBackend.php b/gnokiiSMSBackend.php
new file mode 100644
index 0000000..1a8da93
--- /dev/null
+++ b/gnokiiSMSBackend.php
@@ -0,0 +1,56 @@
+<?php
+require_once 'smsBackend.php';
+class gnokiiSMSBackend implements smsBackend
+{
+    protected $gnokii_path = '/usr/bin/gnokii';
+
+    public function __construct($gnokii_path = null)
+    {
+        if ($gnokii_path !== null)
+        {
+            $this->gnokii_path = $gnokii_path;
+        }
+
+        if (!is_executable($this->gnokii_path))
+        {
+            throw new Exception('Gnokii executable not found (should be at ' . $this->gnokii_path . ')');
+        }
+    }
+
+    /**
+     * sendSMS() Sends an SMS message to the given recipient
+     *
+     * @param String $recipient
+     * @param String $message
+     * @return Boolean
+     */
+    public function sendSMS($recipient, $message)
+    {
+        $descriptors = array(
+            0 => array('pipe', 'r'),
+            1 => array('pipe', 'w'),
+            2 => array('pipe', 'w'),
+        );
+        $cmd = escapeshellcmd($this->gnokii_path) . ' --sendsms ' . escapeshellarg($recipient);
+        $process = proc_open($cmd, $descriptors, $pipes);
+        if (is_resource($process))
+        {
+            fwrite($pipes[0], $message);
+            fclose($pipes[0]);
+
+            $stdout = stream_get_contents($pipes[1]);
+            $stderr = stream_get_contents($pipes[2]);
+
+            $return_value = proc_close($process);
+            if ($return_value != 0)
+            {
+                throw new Exception('Unable to send SMS: ' . $stderr . '; ' . $stdout);
+            }
+        }
+        else
+        {
+            throw new Exception('Unable to send SMS: cannot start gnokii');
+        }
+    }
+}
+
diff --git a/json_sms.php b/json_sms.php
index 95cdaea..bc851f8 100644
--- a/json_sms.php
+++ b/json_sms.php
@@ -2,12 +2,13 @@
 require_once 'jsonRPCServer.php';
 require_once 'smsSender.php';
 require_once 'postgresGatewayBackend.php';
+require_once 'gnokiiSMSBackend.php';
 
 session_start();
 
 try
 {
-    $backend = new postgresGatewayBackend('localhost', 'sms_gateway', 'quaiy8Zu', 'sms_gateway');
+    $dbBackend = new postgresGatewayBackend('localhost', 'sms_gateway', 'quaiy8Zu', 'sms_gateway');
 }
 catch (PDOException $e)
 {
@@ -17,11 +18,21 @@ catch (PDOException $e)
 
 try
 {
-    $smsSender = new smsSender(session_id(), $backend);
+    $smsBackend = new gnokiiSMSBackend();
 }
 catch (Exception $e)
 {
-    header('Status: 500 Internal Server Error (Backend)');
+    header('Status: 500 Internal Server Error (SMS)');
+    exit;
+}
+
+try
+{
+    $smsSender = new smsSender($dbBackend, $smsBackend, session_id());
+}
+catch (Exception $e)
+{
+    header('Status: 500 Internal Server Error');
     exit;
 }
 
diff --git a/postgresGatewayBackend.php b/postgresGatewayBackend.php
index 3e4ae05..a36f5a5 100644
--- a/postgresGatewayBackend.php
+++ b/postgresGatewayBackend.php
@@ -1,61 +1,208 @@
 <?php
 require_once 'gatewayBackend.php';
+require_once 'smsToken.php';
 
 final class postgresGatewayBackend implements gatewayBackend
 {
     const GWBE_SUCCESS  = 0;
     const GWBE_DBERROR  = 1;
     const GWBE_AUTHFAIL = 2;
+    const GWBE_INACTIVE = 3;
+    const GWBE_SERVERR  = 4;
 
     private $dbh = null;
 
     public function __construct($dbHost, $dbUser, $dbPassword, $dbName)
     {
-        $dsn = 'pgsql:host=' . $dbHost . ';dbname=' . $dbName;
-        $this->dbh = new PDO($dsn, $dbUser, $dbPassword);
+        $dsn = 'pgsql:host=' . $dbHost . ';dbname=' . $dbName . ';user=' . $dbUser . ';password=' . $dbPassword;
+        try
+        {
+            $this->dbh = new PDO($dsn, $dbUser, $dbPassword, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
+        }
+        catch (PDOException $e)
+        {
+            error_log('Unable to connect to database: ' . $e->getMessage());
+        }
+    }
+
+    private function tokenExists($token)
+    {
+        $query = 'SELECT id FROM tokens WHERE token = ?';
+        $sth = $this->dbh->prepare($query);
+        $sth->execute($token);
+        $row = $sth->fetch();
+        return ($row !== false);
+    }
+
+    private function generateToken()
+    {
+        do
+        {
+            $str = '                                ';
+            for ($i = 0; $i < 32; $i++)
+                $str[$i] = chr(rand(32, 126));
+            $str = sha1($str);
+        }
+        while ($this->tokenExists($str));
+
+        return $str;
+    }
+
+    protected function refreshToken($token)
+    {
+        try
+        {
+            $query = 'UPDATE tokens SET start_time = NOW() WHERE token = ?';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($token));
+        }
+        catch (PDOException $e)
+        {
+        }
     }
 
     public function getToken($username, $password, $ip, $sessionId)
     {
-        $query = 'SELECT id, password FROM users WHERE username = :username:';
-        $sth = $this->dbh->prepare($query);
-        if ($sth->execute(array(':username:' => $username)))
+        $urec = array();
+        try
         {
-            /*
-            audit_log('Unsuccessful login by $username from $ip');
-            audit_log('Could not create token for $username at $ip');
-            return 'Authentication failed. Reason: Internal Server Error';
-            */
+            $query = 'SELECT id, valid, password FROM users WHERE username = ?';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($username));
+            $urec = $sth->fetch();
+
+            if ($urec === false)
+            {
+                $this->auditLog($ip, 'login', 'Unsuccessful login with unknown username ' . $username);
+                throw new Exception('Authentication failure', self::GWBE_AUTHFAIL);
+            }
+            if ($urec['valid'] == false)
+            {
+                $this->auditLog($ip, 'login', 'Unsuccessful login with disabled username ' . $username);
+                throw new Exception('Authentication failure', self::GWBE_INVALID);
+            }
+            if ($urec['password'] != crypt($password, $urec['password']))
+            {
+                $this->auditLog($ip, 'login', 'Unsuccessful login with bad password for ' . $username);
+                throw new Exception('Authentication failure', self::GWBE_AUTHFAIL);
+            }
         }
-        else
+        catch (PDOException $e)
         {
-            throw new Exception('AuthFail', self::GWBE_DBERROR);
+            throw new Exception('AuthFail: ' . $e->getMessage(), self::GWBE_DBERROR, $e);
         }
+
+        try
+        {
+            $query = 'SELECT ip, token FROM tokens WHERE session_id = ?';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute($sessionId);
+            $row = $sth->fetch();
+            if ($row !== false)
+            {
+                if ($row['ip'] != $ip)
+                {
+                    throw new Exception('Authentication failed. Reason: session used from wrong IP address');
+                }
+                $this->refreshToken($token);
+                return $row['token'];
+            }
+        }
+        catch (PDOException $e)
+        {
+            throw new Exception('Authentication failed. Reason: Internal Server Error', 0, $e);
+        }
+
+        try
+        {
+            $token = $this->generateToken();
+            $query = 'INSERT INTO tokens (ip, session_id, token, start_time, user_id) VALUES (?, ?, ?, NOW(), ?)';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($ip, $sessionId, $token, $urec['id']));
+            $this->auditLog($ip, 'login', 'Successful login by ' . $username);
+            return $token;
+        }
+        catch (PDOException $e)
+        {
+            error_log('Database error: ' . $e->getMessage());
+            $this->auditLog($ip, 'login', 'Unable to save token for ' . $username . ': ' . $e->getMessage());
+            throw new Exception('Authentication failed. Reason: Internal Server Error');
+        }
+
+        /* How did we get here??? */
+        error_log('Unknown Error in getToken()');
+        throw new Exception('Unknown Error');
     }
 
     public function checkToken($token, $sessionId, $ip)
     {
-        return null;
+        try
+        {
+            $query = 'SELECT users.id AS uid, users.username AS uname FROM tokens LEFT JOIN users ON users.id = tokens.user_id WHERE ip = ? AND session_id = ? AND token = ? AND start_time + interval \'1 hour\' > now()';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($ip, $sessionId, $token));
+            $row = $sth->fetch();
+            if ($row === false)
+            {
+                throw new Exception('Authentication failed. Reason: Invalid Token');
+            }
+            $smsToken = new smsToken($row['uid'], $row['uname'], $sessionId, $ip, $token);
+            return $smsToken;
+        }
+        catch (PDOException $e)
+        {
+            throw new Exception('Authentication failed. Reason: Internal Server Error', 0, $e);
+        }
+
+        error_log('Unknown Error in checkToken()');
+        throw new Exception('Authentication failed. Reason: Unknown Error');
     }
 
-    public function removeToken($token)
+    public function removeToken($ip, $sessionId, $token)
     {
-        return null;
-    }
-
-    public function sendSMS($token, $recipient, $message, $passwordLocations)
-    {
-        return null;
+        try
+        {
+            $tokenObj = $this->checkToken($token, $sessionId, $ip);
+            $query = 'DELETE FROM tokens WHERE token = ?';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($token));
+            return $tokenObj->getUserName();
+        }
+        catch (PDOException $e)
+        {
+            throw new Exception('Logout failed. Reasone: Internal Server Error');
+        }
+        catch (Exception $e)
+        {
+            throw new Exception('Authentication failed. Reason: Bad Token');
+        }
     }
 
     public function auditLog($ip, $event, $message)
     {
-        return null;
+        try
+        {
+            $query = 'INSERT INTO audit_log (id, time, ip, event, message) VALUES (DEFAULT, NOW(), ?, ?, ?)';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($ip, $event, $message));
+        }
+        catch (PDOException $e)
+        {
+           error_log('Database error during SMS Audit Logging: ' . $e->getMessage());
+        }
     }
 
-    public function messageLog($recipient, $message, $ip)
+    public function messageLog($senderId, $recipient, $message, $ip)
     {
-        return null;
+        try
+        {
+            $query = 'INSERT INTO log (id, sender, recipient, time, message, ip) VALUES (DEFAULT, ?, ?, NOW(), ?, ?)';
+            $sth = $this->dbh->prepare($query);
+            $sth->execute(array($senderId, $recipient, $message, $ip));
+        }
+        catch (PDOException $e)
+        {
+        }
     }
 }
 
diff --git a/smsBackend.php b/smsBackend.php
new file mode 100644
index 0000000..bc5c3fc
--- /dev/null
+++ b/smsBackend.php
@@ -0,0 +1,6 @@
+<?php
+interface smsBackend
+{
+    public function sendSMS($recipient, $message);
+}
+
diff --git a/smsSender.php b/smsSender.php
index 95cfeae..2d7ea24 100644
--- a/smsSender.php
+++ b/smsSender.php
@@ -1,62 +1,95 @@
 <?php
+require_once 'smsToken.php';
+
 class smsSender
 {
     protected $sessionId = null;
-    protected $backend;
+    protected $dbBackend;
+    protected $smsBackend;
 
-    public function __construct($backend, $sessionId)
+    public function __construct($dbBackend, $smsBackend, $sessionId)
     {
         $this->sessionId = $sessionId;
-        $this->backend = $backend;
+        $this->dbBackend = $dbBackend;
+        $this->smsBackend = $smsBackend;
     }
 
     public function login($username, $password)
     {
+        $token = '';
+
         try
         {
-            $token = $this->backend->getToken($username, $password, $_SERVER['REMOTE_ADDR'], $this->sessionId);
+            $token = $this->dbBackend->getToken($username, $password, $_SERVER['REMOTE_ADDR'], $this->sessionId);
         }
         catch (Exception $e)
         {
             throw new Exception('Authentication failed. Reason: ' . $e->getMessage());
         }
-        $this->backend->auditLog($_SERVER['REMOTE_ADDR'], 'login', 'Successful login by ' . $username);
+        $this->dbBackend->auditLog($_SERVER['REMOTE_ADDR'], 'login', 'Successful login by ' . $username);
         return $token;
     }
 
     public function send($token, $recipient, $message, $passwordLocations)
     {
-        /*
-        if (valid_token($token)
+        try
         {
-            if (send_sms($recipient, $message))
-            {
-                audit_log('Successful message sending by $token->username at $ip');
-                message_log('$message successfully sent to $recipient');
-            }
-            else
-            {
-                audit_log('Message sending failed for $token->username at $ip');
-            }
+            $tokenObj = $this->dbBackend->checkToken($token, $this->sessionId, $_SERVER['REMOTE_ADDR']);
         }
-        else
+        catch (Exception $e)
         {
-            audit_log('Message sending attempt from $ip with invalid token');
-            throw new Exception('Authentication failed. Reason: Invalid Token');
+            $this->dbBackend->auditLog($_SERVER['REMOTE_ADDR'], 'send', 'Message sending attempt by invalid token ' . $token);
+            throw new Exception('Authentication failed. Reason: Bad Token', 0, $e);
         }
-        */
-        /* TODO: implement */
-        throw new Exception('This feature is not yet implemented');
+
+        try
+        {
+            $this->smsBackend->sendSMS($recipient, $message);
+            $this->dbBackend->auditLog($_SERVER['REMOTE_ADDR'], 'send', 'Successful SMS sending by ' . $tokenObj->getUsername());
+            $this->dbBackend->messageLog($tokenObj->getUserId(), $recipient, $this->maskPasswords($message, $passwordLocations), $_SERVER['REMOTE_ADDR']);
+            return 'success';
+        }
+        catch (PDOException $e)
+        {
+            error_log('SMS sending cannot be logged due to a database error!');
+            $this->dbBackend->auditLog($_SERVER['REMOTE_ADDR'], 'send', 'SMS sending by ' . $tokenObj->getUserName() . ' cannot be logged due to a database error');
+        }
+        catch (Exception $e)
+        {
+            $this->dbBackend->auditLog($_SERVER['REMOTE_ADDR'], 'send', 'Error during SMS sending by user ' . $token->getUserName() . ': ' . $e->getMessage());
+            error_log('Error during SMS sending: ' . $e->getMessage());
+        }
+        throw new Exception('Send failed: Unknown Error');
+    }
+
+    protected function maskPasswords($message, $passwordLocations)
+    {
+        $msg = $message;
+
+        foreach ($passwordLocations as $loc)
+        {
+            $msg = substr_replace($msg, '<masked password>', $loc[0], $loc[1]);
+        }
+
+        return $msg;
     }
 
     public function logout($token)
     {
-        /*
-        delete_token($token);
-        audit_log('$token->username logged out at $ip');
-        return 'success';
-        */
-        /* TODO: implement */
-        throw new Exception('This feature is not yet implemented');
+        try
+        {
+            $username = $this->dbBackend->removeToken($_SERVER['REMOTE_ADDR'], $this->sessionId, $token);
+            $this->dbBackend->auditLog($_SERVER['REMOTE_ADDR'], 'logout', $username . ' logged out successfully');
+            session_destroy();
+            session_id('');
+            unset($_COOKIE['PHPSESSID']);
+            return 'success';
+        }
+        catch (Exception $e)
+        {
+            error_log('Logout failed: ' . $e->getMessage());
+            $this->dbBackend->auditLog('Logout failed: ' . $e->getMessage());
+            throw new Exception('Logout failed: Internal Server Error');
+        }
     }
 }
diff --git a/smsToken.php b/smsToken.php
new file mode 100644
index 0000000..15acfd2
--- /dev/null
+++ b/smsToken.php
@@ -0,0 +1,29 @@
+<?php
+class smsToken
+{
+    protected $userId;
+    protected $userName;
+    protected $sessionId;
+    protected $ip;
+    protected $token;
+
+    public function __construct($userId, $userName, $sessionId, $ip, $token)
+    {
+        $this->userId    = $userId;
+        $this->userName  = $userName;
+        $this->sessionId = $sessionId;
+        $this->ip        = $ip;
+        $this->token     = $token;
+    }
+
+    public function getUserId()
+    {
+        return $this->userId;
+    }
+
+    public function getUserName()
+    {
+        return $this->userName;
+    }
+}
+