diff --git a/src/close.rs b/src/close.rs
index 783c650..3f41f40 100644
--- a/src/close.rs
+++ b/src/close.rs
@@ -58,4 +58,7 @@ impl Close {
     pub fn parse(json: &str) -> Result<Close> {
         serde_json::from_str(json).map_err(|e| Error::JsonParseFailed(e))
     }
+    pub fn get_id(&self) -> String {
+        self.id.clone()
+    }
 }
diff --git a/src/proto.rs b/src/proto.rs
index 0931a35..1ac75ce 100644
--- a/src/proto.rs
+++ b/src/proto.rs
@@ -14,6 +14,8 @@ pub struct Proto {
     max_subs: usize,
 }
 
+const MAX_SUBSCRIPTION_ID_LEN: usize = 256;
+
 impl Proto {
     pub fn new() -> Self {
         let p = Proto {
@@ -35,10 +37,34 @@ impl Proto {
     }
 
     pub fn subscribe(&mut self, s: Subscription) {
-        unimplemented!();
+        // TODO: add NOTICE responses for error conditions.  At the
+        // moment, we are silently dropping subscription requests that
+        // aren't perfect.
+
+        // check if the subscription key is reasonable.
+        let k = s.get_id();
+        let sub_id_len = k.len();
+        if sub_id_len > MAX_SUBSCRIPTION_ID_LEN {
+            info!("Dropping subscription with huge ({}) length", sub_id_len);
+            return;
+        }
+        // check if an existing subscription exists.
+        if self.subscriptions.contains_key(&k) {
+            info!("Client requested a subscription with an already-existing key");
+            return;
+        }
+
+        // check if there is room for another subscription.
+        if self.subscriptions.len() >= self.max_subs {
+            info!("Client has reached the maximum number of unique subscriptions");
+            return;
+        }
+        // add subscription
+        self.subscriptions.insert(k, s);
     }
 
     pub fn unsubscribe(&mut self, c: Close) {
+        self.subscriptions.remove(&c.get_id());
         unimplemented!();
     }
 }
diff --git a/src/subscription.rs b/src/subscription.rs
index 367ebcf..ad9fdf5 100644
--- a/src/subscription.rs
+++ b/src/subscription.rs
@@ -83,6 +83,9 @@ impl Subscription {
     pub fn parse(json: &str) -> Result<Subscription> {
         serde_json::from_str(json).map_err(|e| Error::JsonParseFailed(e))
     }
+    pub fn get_id(&self) -> String {
+        self.id.clone()
+    }
 }
 
 #[cfg(test)]