diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..3dec5d5
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,119 @@
+use rand::distributions::{Alphanumeric, DistString};
+use std::{
+    sync::mpsc::{channel, Sender},
+    thread::spawn,
+};
+
+pub enum Session {
+    Ok,
+    New(String),
+}
+
+struct ValidateSession {
+    id: Option<String>,
+    tx: Sender<Session>,
+}
+
+impl ValidateSession {
+    fn new(id: Option<String>, tx: Sender<Session>) -> Self {
+        Self { id: id, tx: tx }
+    }
+}
+
+enum SendMsg {
+    ValidateSess(ValidateSession),
+}
+
+#[derive(Clone)]
+pub struct MoreThanText {
+    tx: Sender<SendMsg>,
+}
+
+impl MoreThanText {
+    pub fn new() -> Self {
+        let (tx, rx) = channel();
+        spawn(move || {
+            let mut ids: Vec<String> = Vec::new();
+            loop {
+                match rx.recv().unwrap() {
+                    SendMsg::ValidateSess(vsess) => {
+                        let session: Session;
+                        match vsess.id {
+                            Some(id) => {
+                                if ids.contains(&id) {
+                                    session = Session::Ok;
+                                } else {
+                                    let sid =
+                                        Alphanumeric.sample_string(&mut rand::thread_rng(), 16);
+                                    ids.push(sid.clone());
+                                    session = Session::New(sid);
+                                }
+                            }
+                            None => {
+                                let sid = Alphanumeric.sample_string(&mut rand::thread_rng(), 16);
+                                ids.push(sid.clone());
+                                session = Session::New(sid);
+                            }
+                        }
+                        vsess.tx.send(session).unwrap();
+                    }
+                }
+            }
+        });
+        Self { tx: tx }
+    }
+
+    pub fn get_session(&self, id: Option<String>) -> Session {
+        let (tx, rx) = channel();
+        self.tx
+            .send(SendMsg::ValidateSess(ValidateSession::new(id, tx)))
+            .unwrap();
+        rx.recv().unwrap()
+    }
+}
+
+#[cfg(test)]
+mod client {
+    use super::*;
+
+    #[test]
+    fn session_ids_are_unique() {
+        let conn = MoreThanText::new();
+        let mut ids: Vec<String> = Vec::new();
+        for _ in 1..10 {
+            match conn.get_session(None) {
+                Session::New(id) => {
+                    if ids.contains(&id) {
+                        assert!(false, "{} is a duplicate id", id);
+                    }
+                    ids.push(id)
+                }
+                Session::Ok => assert!(false, "Should have returned a new id."),
+            }
+        }
+    }
+
+    #[test]
+    fn existing_ids_return_ok() {
+        let conn = MoreThanText::new();
+        let sid: String;
+        match conn.get_session(None) {
+            Session::New(id) => sid = id,
+            Session::Ok => unreachable!(),
+        }
+        match conn.get_session(Some(sid.clone())) {
+            Session::New(_) => assert!(false, "should not create a new session"),
+            Session::Ok => {}
+        }
+    }
+
+    #[test]
+    fn bad_ids_get_new_session() {
+        let conn = MoreThanText::new();
+        let sid = "bad id";
+        match conn.get_session(Some(sid.to_string())) {
+            Session::New(id) => assert_ne!(sid, id, "do not reuse original id"),
+            Session::Ok => assert!(false, "shouuld generate a new id"),
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 2d4a0ad..3302686 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,7 @@
-use axum::{response::IntoResponse, routing::get, Router};
+use axum::{extract::State, response::IntoResponse, routing::get, Router};
 use axum_extra::extract::cookie::{Cookie, CookieJar};
 use clap::Parser;
-use rand::distributions::{Alphanumeric, DistString};
+use morethantext::{MoreThanText, Session};
 
 const LOCALHOST: &str = "127.0.0.1";
 const SESSION_KEY: &str = "sessionid";
@@ -29,26 +29,27 @@ mod http_session {
 async fn main() {
     let args = Args::parse();
     let addr = format!("{}:{}", args.address, args.port);
-    let app = Router::new().route("/", get(handler));
+    let state = MoreThanText::new();
+    let app = Router::new().route("/", get(handler)).with_state(state);
     let listener = tokio::net::TcpListener::bind(&addr).await.unwrap();
     axum::serve(listener, app.into_make_service())
         .await
         .unwrap();
 }
 
-async fn handler(jar: CookieJar) -> impl IntoResponse {
+async fn handler(jar: CookieJar, state: State<MoreThanText>) -> impl IntoResponse {
     let cookies: CookieJar;
-    let id: String;
+    let sid: Option<String>;
     match jar.get(SESSION_KEY) {
-        Some(session) => {
-            id = session.to_string();
-            cookies = jar;
-        }
-        None => {
-            id = Alphanumeric.sample_string(&mut rand::thread_rng(), 16);
+        Some(cookie) => sid = Some(cookie.value().to_string()),
+        None => sid = None,
+    }
+    match state.get_session(sid) {
+        Session::Ok => cookies = jar,
+        Session::New(id) => {
             let cookie = Cookie::build((SESSION_KEY, id.clone())).domain("example.com");
             cookies = jar.add(cookie);
         }
     }
-    (cookies, format!("id is {}", id))
+    (cookies, "Something goes here.")
 }
diff --git a/test/test_single_boot.py b/test/test_single_boot.py
index b81c0c9..fa4cf4a 100644
--- a/test/test_single_boot.py
+++ b/test/test_single_boot.py
@@ -74,3 +74,14 @@ class BootUpTC(MTTClusterTC):
         for _ in range(2):
             await self.run_tests("/", tests)
         self.assertEqual(len(ids), 1)
+
+    async def test_reset_bad_session_id(self):
+        """Does the session id get reset if bad or expired?"""
+        await self.create_server()
+        value = "bad id"
+        async with ClientSession() as session:
+            async with session.get(
+                f"{self.servers[0].host}/", cookies={SESSION_KEY: value}
+            ) as response:
+                self.assertIn(SESSION_KEY, response.cookies)
+                self.assertNotEqual(response.cookies[SESSION_KEY].value, value)