diff --git a/services/tunnelbroker/src/cxx_bridge.rs b/services/tunnelbroker/src/cxx_bridge.rs
index f9eeb0f2b..21ef93388 100644
--- a/services/tunnelbroker/src/cxx_bridge.rs
+++ b/services/tunnelbroker/src/cxx_bridge.rs
@@ -1,69 +1,78 @@
 #[cxx::bridge]
 pub mod ffi {
   enum GRPCStatusCodes {
     Ok,
     Cancelled,
     Unknown,
     InvalidArgument,
     DeadlineExceeded,
     NotFound,
     AlreadyExists,
     PermissionDenied,
     ResourceExhausted,
     FailedPrecondition,
     Aborted,
     OutOfRange,
     Unimplemented,
     Internal,
     Unavailable,
     DataLoss,
     Unauthenticated,
   }
   struct GrpcResult {
     statusCode: GRPCStatusCodes,
     errorText: String,
   }
   struct SessionSignatureResult {
     toSign: String,
     grpcStatus: GrpcResult,
   }
   struct NewSessionResult {
     sessionID: String,
     grpcStatus: GrpcResult,
   }
   struct SessionItem {
     deviceID: String,
     publicKey: String,
     notifyToken: String,
     deviceType: i32,
     appVersion: String,
     deviceOS: String,
     isOnline: bool,
   }
+  struct MessageItem {
+    messageID: String,
+    fromDeviceID: String,
+    toDeviceID: String,
+    payload: String,
+    blobHashes: String,
+  }
 
   unsafe extern "C++" {
     include!("tunnelbroker/src/libcpp/Tunnelbroker.h");
     pub fn initialize();
     pub fn getConfigParameter(parameter: &str) -> Result<String>;
     pub fn isSandbox() -> Result<bool>;
     pub fn sessionSignatureHandler(deviceID: &str) -> SessionSignatureResult;
     pub fn newSessionHandler(
       deviceID: &str,
       publicKey: &str,
       signature: &str,
       deviceType: i32,
       deviceAppVersion: &str,
       deviceOS: &str,
       notifyToken: &str,
     ) -> NewSessionResult;
     pub fn getSessionItem(sessionID: &str) -> Result<SessionItem>;
     pub fn updateSessionItemIsOnline(
       sessionID: &str,
       isOnline: bool,
     ) -> Result<()>;
     pub fn updateSessionItemDeviceToken(
       sessionID: &str,
       newNotifToken: &str,
     ) -> Result<()>;
+    pub fn getMessagesFromDatabase(deviceID: &str) -> Result<Vec<MessageItem>>;
+    pub fn eraseMessagesFromAMQP(deviceID: &str) -> Result<()>;
   }
 }
diff --git a/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp b/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp
index e8a7042ac..3a39e9896 100644
--- a/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp
+++ b/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp
@@ -1,185 +1,207 @@
 #include "Tunnelbroker.h"
 #include "AmqpManager.h"
 #include "AwsTools.h"
 #include "ConfigManager.h"
 #include "CryptoTools.h"
 #include "DatabaseManager.h"
+#include "DeliveryBroker.h"
 #include "GlobalTools.h"
 #include "Tools.h"
 
 #include "rust/cxx.h"
 #include "tunnelbroker/src/cxx_bridge.rs.h"
 
 #include <glog/logging.h>
 
 void initialize() {
   comm::network::tools::InitLogging("tunnelbroker");
   comm::network::config::ConfigManager::getInstance().load();
   Aws::InitAPI({});
   // List of AWS DynamoDB tables to check if they are created and can be
   // accessed before any AWS API methods
   const std::list<std::string> tablesList = {
       comm::network::config::ConfigManager::getInstance().getParameter(
           comm::network::config::ConfigManager::OPTION_DYNAMODB_SESSIONS_TABLE),
       comm::network::config::ConfigManager::getInstance().getParameter(
           comm::network::config::ConfigManager::
               OPTION_DYNAMODB_SESSIONS_VERIFICATION_TABLE),
       comm::network::config::ConfigManager::getInstance().getParameter(
           comm::network::config::ConfigManager::
               OPTION_DYNAMODB_SESSIONS_PUBLIC_KEY_TABLE),
       comm::network::config::ConfigManager::getInstance().getParameter(
           comm::network::config::ConfigManager::
               OPTION_DYNAMODB_MESSAGES_TABLE)};
   for (const std::string &table : tablesList) {
     if (!comm::network::database::DatabaseManager::getInstance()
              .isTableAvailable(table)) {
       throw std::runtime_error(
           "Error: AWS DynamoDB table '" + table + "' is not available");
     }
   };
   comm::network::AmqpManager::getInstance().init();
 }
 
 rust::String getConfigParameter(rust::Str parameter) {
   return rust::String{
       comm::network::config::ConfigManager::getInstance().getParameter(
           std::string{parameter})};
 }
 
 bool isSandbox() {
   return comm::network::tools::isSandbox();
 }
 
 SessionSignatureResult sessionSignatureHandler(rust::Str deviceID) {
   const std::string requestedDeviceID(deviceID);
   if (!comm::network::tools::validateDeviceID(requestedDeviceID)) {
     return SessionSignatureResult{
         .grpcStatus = {
             .statusCode = GRPCStatusCodes::InvalidArgument,
             .errorText =
                 "Format validation failed for deviceID: " + requestedDeviceID}};
   }
   const std::string toSign = comm::network::tools::generateRandomString(
       comm::network::SIGNATURE_REQUEST_LENGTH);
   std::shared_ptr<comm::network::database::SessionSignItem> SessionSignItem =
       std::make_shared<comm::network::database::SessionSignItem>(
           toSign, requestedDeviceID);
   comm::network::database::DatabaseManager::getInstance().putSessionSignItem(
       *SessionSignItem);
 
   return SessionSignatureResult{
       .toSign = toSign, .grpcStatus = {.statusCode = GRPCStatusCodes::Ok}};
 }
 
 NewSessionResult newSessionHandler(
     rust::Str deviceID,
     rust::Str publicKey,
     rust::Str signature,
     int32_t deviceType,
     rust::Str deviceAppVersion,
     rust::Str deviceOS,
     rust::Str notifyToken) {
   std::shared_ptr<comm::network::database::DeviceSessionItem> deviceSessionItem;
   std::shared_ptr<comm::network::database::SessionSignItem> sessionSignItem;
   std::shared_ptr<comm::network::database::PublicKeyItem> publicKeyItem;
   const std::string stringDeviceID{deviceID};
   if (!comm::network::tools::validateDeviceID(stringDeviceID)) {
     return NewSessionResult{
         .grpcStatus = {
             .statusCode = GRPCStatusCodes::InvalidArgument,
             .errorText = "Format validation failed for deviceID"}};
   }
   const std::string stringPublicKey{publicKey};
   const std::string newSessionID = comm::network::tools::generateUUID();
   try {
     sessionSignItem = comm::network::database::DatabaseManager::getInstance()
                           .findSessionSignItem(stringDeviceID);
     if (sessionSignItem == nullptr) {
       return NewSessionResult{
           .grpcStatus = {
               .statusCode = GRPCStatusCodes::NotFound,
               .errorText = "Session signature request not found for deviceID"}};
     }
     publicKeyItem = comm::network::database::DatabaseManager::getInstance()
                         .findPublicKeyItem(stringDeviceID);
     if (publicKeyItem == nullptr) {
       std::shared_ptr<comm::network::database::PublicKeyItem> newPublicKeyItem =
           std::make_shared<comm::network::database::PublicKeyItem>(
               stringDeviceID, stringPublicKey);
       comm::network::database::DatabaseManager::getInstance().putPublicKeyItem(
           *newPublicKeyItem);
     } else if (stringPublicKey != publicKeyItem->getPublicKey()) {
       return NewSessionResult{
           .grpcStatus = {
               .statusCode = GRPCStatusCodes::PermissionDenied,
               .errorText = "The public key doesn't match for deviceID"}};
     }
     const std::string verificationMessage = sessionSignItem->getSign();
     if (!comm::network::crypto::rsaVerifyString(
             stringPublicKey, verificationMessage, std::string{signature})) {
       return NewSessionResult{
           .grpcStatus = {
               .statusCode = GRPCStatusCodes::PermissionDenied,
               .errorText =
                   "Signature for the verification message is not valid"}};
     }
     comm::network::database::DatabaseManager::getInstance()
         .removeSessionSignItem(stringDeviceID);
 
     deviceSessionItem =
         std::make_shared<comm::network::database::DeviceSessionItem>(
             newSessionID,
             stringDeviceID,
             stringPublicKey,
             std::string{notifyToken},
             deviceType,
             std::string{deviceAppVersion},
             std::string{deviceOS});
     comm::network::database::DatabaseManager::getInstance().putSessionItem(
         *deviceSessionItem);
   } catch (std::runtime_error &e) {
     LOG(ERROR) << "gRPC: "
                << "Error while processing 'NewSession' request: " << e.what();
     return NewSessionResult{
         .grpcStatus = {
             .statusCode = GRPCStatusCodes::Internal, .errorText = e.what()}};
   }
   return NewSessionResult{
       .sessionID = newSessionID,
       .grpcStatus = {.statusCode = GRPCStatusCodes::Ok}};
 }
 
 SessionItem getSessionItem(rust::Str sessionID) {
   const std::string stringSessionID = std::string{sessionID};
   if (!comm::network::tools::validateSessionID(stringSessionID)) {
     throw std::invalid_argument("Invalid format for 'sessionID'");
   }
   std::shared_ptr<comm::network::database::DeviceSessionItem> sessionItem =
       comm::network::database::DatabaseManager::getInstance().findSessionItem(
           stringSessionID);
   if (sessionItem == nullptr) {
     throw std::invalid_argument(
         "No sessions found for 'sessionID': " + stringSessionID);
   }
   return SessionItem{
       .deviceID = sessionItem->getDeviceID(),
       .publicKey = sessionItem->getPubKey(),
       .notifyToken = sessionItem->getNotifyToken(),
       .deviceType = static_cast<int>(sessionItem->getDeviceType()),
       .appVersion = sessionItem->getAppVersion(),
       .deviceOS = sessionItem->getDeviceOs(),
       .isOnline = sessionItem->getIsOnline()};
 }
 
 void updateSessionItemIsOnline(rust::Str sessionID, bool isOnline) {
   comm::network::database::DatabaseManager::getInstance()
       .updateSessionItemIsOnline(std::string{sessionID}, isOnline);
 }
 
 void updateSessionItemDeviceToken(
     rust::Str sessionID,
     rust::Str newNotifToken) {
   comm::network::database::DatabaseManager::getInstance()
       .updateSessionItemDeviceToken(
           std::string{sessionID}, std::string{newNotifToken});
 }
+
+rust::Vec<MessageItem> getMessagesFromDatabase(rust::Str deviceID) {
+  std::vector<std::shared_ptr<comm::network::database::MessageItem>>
+      messagesFromDatabase =
+          comm::network::database::DatabaseManager::getInstance()
+              .findMessageItemsByReceiver(std::string{deviceID});
+  rust::Vec<MessageItem> result;
+  for (auto &messageFromDatabase : messagesFromDatabase) {
+    result.push_back(MessageItem{
+        .messageID = messageFromDatabase->getMessageID(),
+        .fromDeviceID = messageFromDatabase->getFromDeviceID(),
+        .payload = messageFromDatabase->getPayload(),
+        .blobHashes = messageFromDatabase->getBlobHashes(),
+    });
+  }
+  return result;
+}
+
+void eraseMessagesFromAMQP(rust::Str deviceID) {
+  comm::network::DeliveryBroker::getInstance().erase(std::string{deviceID});
+}
diff --git a/services/tunnelbroker/src/libcpp/Tunnelbroker.h b/services/tunnelbroker/src/libcpp/Tunnelbroker.h
index 136141452..5311dab5f 100644
--- a/services/tunnelbroker/src/libcpp/Tunnelbroker.h
+++ b/services/tunnelbroker/src/libcpp/Tunnelbroker.h
@@ -1,20 +1,22 @@
 #pragma once
 
 #include "rust/cxx.h"
 #include "tunnelbroker/src/cxx_bridge.rs.h"
 
 void initialize();
 rust::String getConfigParameter(rust::Str parameter);
 bool isSandbox();
 SessionSignatureResult sessionSignatureHandler(rust::Str deviceID);
 NewSessionResult newSessionHandler(
     rust::Str deviceID,
     rust::Str publicKey,
     rust::Str signature,
     int32_t deviceType,
     rust::Str deviceAppVersion,
     rust::Str deviceOS,
     rust::Str notifyToken);
 SessionItem getSessionItem(rust::Str sessionID);
 void updateSessionItemIsOnline(rust::Str sessionID, bool isOnline);
 void updateSessionItemDeviceToken(rust::Str sessionID, rust::Str newNotifToken);
+rust::Vec<MessageItem> getMessagesFromDatabase(rust::Str deviceID);
+void eraseMessagesFromAMQP(rust::Str deviceID);
diff --git a/services/tunnelbroker/src/server/mod.rs b/services/tunnelbroker/src/server/mod.rs
index 7c1dc0197..405e03e92 100644
--- a/services/tunnelbroker/src/server/mod.rs
+++ b/services/tunnelbroker/src/server/mod.rs
@@ -1,281 +1,322 @@
 use super::constants;
 use super::cxx_bridge::ffi::{
-  getSessionItem, newSessionHandler, sessionSignatureHandler,
-  updateSessionItemDeviceToken, updateSessionItemIsOnline, GRPCStatusCodes,
+  eraseMessagesFromAMQP, getMessagesFromDatabase, getSessionItem,
+  newSessionHandler, sessionSignatureHandler, updateSessionItemDeviceToken,
+  updateSessionItemIsOnline, GRPCStatusCodes,
 };
 use anyhow::Result;
 use futures::Stream;
 use std::pin::Pin;
 use tokio::sync::mpsc;
 use tokio::time::{sleep, Duration};
 use tokio_stream::{wrappers::ReceiverStream, StreamExt};
 use tonic::{transport::Server, Request, Response, Status, Streaming};
 use tracing::{debug, error};
 use tunnelbroker::message_to_tunnelbroker::Data::{
   MessagesToSend, NewNotifyToken, ProcessedMessages,
 };
 use tunnelbroker::tunnelbroker_service_server::{
   TunnelbrokerService, TunnelbrokerServiceServer,
 };
 mod tools;
 mod tunnelbroker {
   tonic::include_proto!("tunnelbroker");
 }
 
 #[derive(Debug, Default)]
 struct TunnelbrokerServiceHandlers {}
 
 #[tonic::async_trait]
 impl TunnelbrokerService for TunnelbrokerServiceHandlers {
   async fn session_signature(
     &self,
     request: Request<tunnelbroker::SessionSignatureRequest>,
   ) -> Result<Response<tunnelbroker::SessionSignatureResponse>, Status> {
     let result = sessionSignatureHandler(&request.into_inner().device_id);
     if result.grpcStatus.statusCode != GRPCStatusCodes::Ok {
       return Err(tools::create_tonic_status(
         result.grpcStatus.statusCode,
         &result.grpcStatus.errorText,
       ));
     }
     Ok(Response::new(tunnelbroker::SessionSignatureResponse {
       to_sign: result.toSign,
     }))
   }
 
   async fn new_session(
     &self,
     request: Request<tunnelbroker::NewSessionRequest>,
   ) -> Result<Response<tunnelbroker::NewSessionResponse>, Status> {
     let inner_request = request.into_inner();
     let notify_token = inner_request.notify_token.unwrap_or(String::new());
     if !tunnelbroker::new_session_request::DeviceTypes::is_valid(
       inner_request.device_type,
     ) {
       return Err(tools::create_tonic_status(
         GRPCStatusCodes::InvalidArgument,
         "Unsupported device type",
       ));
     };
 
     let result = newSessionHandler(
       &inner_request.device_id,
       &inner_request.public_key,
       &inner_request.signature,
       inner_request.device_type,
       &inner_request.device_app_version,
       &inner_request.device_os,
       &notify_token,
     );
     if result.grpcStatus.statusCode != GRPCStatusCodes::Ok {
       return Err(tools::create_tonic_status(
         result.grpcStatus.statusCode,
         &result.grpcStatus.errorText,
       ));
     }
     Ok(Response::new(tunnelbroker::NewSessionResponse {
       session_id: result.sessionID,
     }))
   }
 
   type MessagesStreamStream = Pin<
     Box<
       dyn Stream<Item = Result<tunnelbroker::MessageToClient, Status>> + Send,
     >,
   >;
 
   async fn messages_stream(
     &self,
     request: Request<Streaming<tunnelbroker::MessageToTunnelbroker>>,
   ) -> Result<Response<Self::MessagesStreamStream>, Status> {
     let session_id = match request.metadata().get("sessionID") {
       Some(metadata_session_id) => metadata_session_id
         .to_str()
         .expect("metadata session id was not valid UTF8")
         .to_string(),
       None => {
         return Err(Status::invalid_argument(
           "No 'sessionID' in metadata was provided",
         ))
       }
     };
     let session_item = match getSessionItem(&session_id) {
       Ok(database_item) => database_item,
       Err(err) => return Err(Status::unauthenticated(err.what())),
     };
 
     let (tx, rx) = mpsc::channel(constants::GRPC_TX_QUEUE_SIZE);
 
     // Through this function, we will write to the output stream from different Tokio
     // tasks and update the device's online status if the write was unsuccessful
     async fn tx_writer<T>(
       session_id: &str,
       channel: &tokio::sync::mpsc::Sender<T>,
       payload: T,
     ) -> Result<(), String> {
       let result = channel.send(payload).await;
       match result {
         Ok(result) => Ok(result),
         Err(err) => {
           if let Err(err) = updateSessionItemIsOnline(&session_id, false) {
             return Err(err.what().to_string());
           }
           return Err(err.to_string());
         }
       }
     }
 
     if let Err(err) = updateSessionItemIsOnline(&session_id, true) {
       return Err(Status::internal(err.what()));
     }
 
     // Checking for an empty notif token and requesting the new one from the client
     if session_item.notifyToken.is_empty()
       && session_item.deviceType
         == tunnelbroker::new_session_request::DeviceTypes::Mobile as i32
     {
       let result = tx_writer(
         &session_id,
         &tx,
         Ok(tunnelbroker::MessageToClient {
           data: Some(
             tunnelbroker::message_to_client::Data::NewNotifyTokenRequired(()),
           ),
         }),
       );
       if let Err(err) = result.await {
         debug!(
           "Error while sending notification token request to the client: {}",
           err
         );
       };
     }
 
+    // When a client connects to the bidirectional messages stream, first we check
+    // if there are undelivered messages in the database
+    let messages_from_database =
+      match getMessagesFromDatabase(&session_item.deviceID) {
+        Ok(messages) => messages,
+        Err(err) => return Err(Status::internal(err.what())),
+      };
+    if messages_from_database.len() > 0 {
+      if let Err(err) = eraseMessagesFromAMQP(&session_item.deviceID) {
+        return Err(Status::internal(err.what()));
+      };
+      let mut messages_to_response = vec![];
+      for message in &messages_from_database {
+        messages_to_response.push(tunnelbroker::MessageToClientStruct {
+          message_id: message.messageID.clone(),
+          from_device_id: message.fromDeviceID.clone(),
+          payload: message.payload.clone(),
+          blob_hashes: vec![message.blobHashes.clone()],
+        });
+      }
+      let result_from_writer = tx_writer(
+        &session_id,
+        &tx,
+        Ok(tunnelbroker::MessageToClient {
+          data: Some(tunnelbroker::message_to_client::Data::MessagesToDeliver(
+            tunnelbroker::MessagesToDeliver {
+              messages: messages_to_response,
+            },
+          )),
+        }),
+      );
+      if let Err(err) = result_from_writer.await {
+        debug!(
+          "Error while sending undelivered messages from database to the client: {}",
+          err
+        );
+        return Err(Status::aborted(err));
+      };
+    }
+
     // Spawning asynchronous Tokio task with the client pinging loop inside to
     // make sure that the client is online
     tokio::spawn({
       let session_id = session_id.clone();
       let tx = tx.clone();
       async move {
         loop {
           sleep(Duration::from_millis(constants::GRPC_PING_INTERVAL_MS)).await;
           let result = tx_writer(
             &session_id,
             &tx,
             Ok(tunnelbroker::MessageToClient {
               data: Some(tunnelbroker::message_to_client::Data::Ping(())),
             }),
           );
           if let Err(err) = result.await {
             debug!("Failed to write ping to a channel: {}", err);
             break;
           };
         }
       }
     });
 
     let mut input_stream = request.into_inner();
     // Spawning asynchronous Tokio task for handling incoming messages from the client
     tokio::spawn(async move {
       while let Some(result) = input_stream.next().await {
         if let Err(err) = result {
           debug!("Error in input stream: {}", err);
           break;
         }
         if let Some(message_data) = result.unwrap().data {
           match message_data {
             NewNotifyToken(new_token) => {
               if let Err(err) =
                 updateSessionItemDeviceToken(&session_id, &new_token)
               {
                 error!(
                   "Error in updating the device notification token in the database: {}",
                   err.what()
                 );
                 let writer_result = tx_writer(
                   &session_id,
                   &tx,
                   Err(
                     Status::internal(
                       "Error in updating the device notification token in the database"
                     )
                   ),
                 );
                 if let Err(err) = writer_result.await {
                   debug!(
                     "Failed to write internal error to a channel: {}",
                     err
                   );
                 };
               }
             }
             MessagesToSend(_) => (),
             ProcessedMessages(_) => (),
           }
         }
       }
       if let Err(err) = updateSessionItemIsOnline(&session_id, false) {
         error!(
           "Error in updating the session online state in the database: {}",
           err.what()
         );
       }
     });
 
     let output_stream = ReceiverStream::new(rx);
     Ok(Response::new(
       Box::pin(output_stream) as Self::MessagesStreamStream
     ))
   }
 
   // These empty old API handlers are deprecated and should be removed.
   // They are implemented only to fix the building process.
   async fn check_if_primary_device_online(
     &self,
     _request: Request<tunnelbroker::CheckRequest>,
   ) -> Result<Response<tunnelbroker::CheckResponse>, Status> {
     Err(Status::cancelled("Deprecated"))
   }
 
   async fn become_new_primary_device(
     &self,
     _request: Request<tunnelbroker::NewPrimaryRequest>,
   ) -> Result<Response<tunnelbroker::NewPrimaryResponse>, Status> {
     Err(Status::cancelled("Deprecated"))
   }
 
   async fn send_pong(
     &self,
     _request: Request<tunnelbroker::PongRequest>,
   ) -> Result<Response<()>, Status> {
     Err(Status::cancelled("Deprecated"))
   }
 
   async fn send(
     &self,
     _request: Request<tunnelbroker::SendRequest>,
   ) -> Result<Response<()>, Status> {
     Err(Status::cancelled("Deprecated"))
   }
 
   type GetStream = Pin<
     Box<dyn Stream<Item = Result<tunnelbroker::GetResponse, Status>> + Send>,
   >;
   async fn get(
     &self,
     _request: Request<tunnelbroker::GetRequest>,
   ) -> Result<Response<Self::GetStream>, Status> {
     Err(Status::cancelled("Deprecated"))
   }
 }
 
 pub async fn run_grpc_server() -> Result<()> {
   let addr = format!("[::1]:{}", constants::GRPC_SERVER_PORT).parse()?;
   Server::builder()
     .add_service(TunnelbrokerServiceServer::new(
       TunnelbrokerServiceHandlers::default(),
     ))
     .serve(addr)
     .await?;
   Ok(())
 }