diff --git a/src/signal_negotiation.cpp b/src/signal_negotiation.cpp
index 5fe1eb2..65c4225 100644
--- a/src/signal_negotiation.cpp
+++ b/src/signal_negotiation.cpp
@@ -168,6 +168,63 @@ bool SignalNegotiation::query_user_id_list(websocketpp::connection_hdl hdl,
   return true;
 }
 
+bool SignalNegotiation::join_transmission(websocketpp::connection_hdl hdl,
+                                          const json& j) {
+  std::string transmission_id_pwd = j["transmission_id"].get<std::string>();
+  std::string transmission_id;
+  std::string password;
+
+  if (transmission_id_pwd.find("@") != std::string::npos) {
+    transmission_id =
+        transmission_id_pwd.substr(0, transmission_id_pwd.find("@"));
+    password = transmission_id_pwd.substr(transmission_id_pwd.find("@") + 1);
+  } else {
+    transmission_id = transmission_id_pwd;
+    password = "";
+  }
+
+  std::string user_id = j["user_id"].get<std::string>();
+  LOG_INFO("[{}] joins transmission [{}]", user_id.c_str(),
+           transmission_id.c_str());
+
+  int ret = device_db_manager_->VerifyDevice(transmission_id, password);
+
+  if (0 == ret) {
+    transmission_manager_->BindGuestToTransmission(user_id, transmission_id);
+
+    json message = {{"type", "user_join_transmission"},
+                    {"transmission_id", transmission_id},
+                    {"user_id", user_id},
+                    {"status", "success"}};
+
+    std::string host_id =
+        transmission_manager_->GetHostIdOfTransmission(transmission_id);
+
+    if (!host_id.empty()) {
+      send_msg_(transmission_manager_->GetWsHandle(host_id), message);
+    }
+  } else if (-1 == ret) {
+    LOG_ERROR("Password incorrect for transmission id [{}]",
+              transmission_id.c_str());
+    json message = {{"type", "user_join_transmission"},
+                    {"transmission_id", transmission_id},
+                    {"status", "failed"},
+                    {"reason", "Incorrect password"}};
+
+    send_msg_(hdl, message);
+  } else if (-2 == ret) {
+    LOG_ERROR("No such transmission id [{}]", transmission_id.c_str());
+    json message = {{"type", "user_join_transmission"},
+                    {"transmission_id", transmission_id},
+                    {"status", "failed"},
+                    {"reason", "No such transmission id"}};
+
+    send_msg_(hdl, message);
+  }
+
+  return true;
+}
+
 bool SignalNegotiation::offer(websocketpp::connection_hdl hdl, const json& j) {
   std::string transmission_id = j["transmission_id"].get<std::string>();
   std::string remote_user_id = j["remote_user_id"].get<std::string>();
diff --git a/src/signal_negotiation.h b/src/signal_negotiation.h
index 7f4099d..3cd44ec 100644
--- a/src/signal_negotiation.h
+++ b/src/signal_negotiation.h
@@ -28,6 +28,8 @@ class SignalNegotiation {
   bool login_user(websocketpp::connection_hdl hdl, const json& j);
   bool leave_transmission(websocketpp::connection_hdl hdl, const json& j);
   bool query_user_id_list(websocketpp::connection_hdl hdl, const json& j);
+  bool join_transmission(websocketpp::connection_hdl hdl,
+                                          const json& j);
   bool offer(websocketpp::connection_hdl hdl, const json& j);
   bool answer(websocketpp::connection_hdl hdl, const json& j);
   bool new_candidate(websocketpp::connection_hdl hdl, const json& j);
diff --git a/src/signal_server.cpp b/src/signal_server.cpp
index 5dad4ef..e46fcf8 100644
--- a/src/signal_server.cpp
+++ b/src/signal_server.cpp
@@ -182,6 +182,9 @@ void SignalServer::OnMessage(websocketpp::connection_hdl hdl,
     case "query_user_id_list"_H:
       signal_negotiation_->query_user_id_list(hdl, j);
       break;
+    case "join_transmission"_H:
+      signal_negotiation_->join_transmission(hdl, j);
+      break;
     case "offer"_H:
       signal_negotiation_->offer(hdl, j);
       break;
diff --git a/src/transmission_manager.cpp b/src/transmission_manager.cpp
index aa1ad24..86df0d5 100644
--- a/src/transmission_manager.cpp
+++ b/src/transmission_manager.cpp
@@ -71,6 +71,16 @@ std::vector<std::string> TransmissionManager::GetAllUserIdOfTransmission(
   return result;
 }
 
+std::string TransmissionManager::GetHostIdOfTransmission(
+    const std::string& transmission_id) {
+  std::lock_guard<std::recursive_mutex> lock(ws_hdl_alive_checker_mutex_);
+  if (transmission_host_id_list_.count(transmission_id)) {
+    return transmission_host_id_list_[transmission_id];
+  }
+
+  return "";
+}
+
 bool TransmissionManager::BindHostToTransmission(
     const std::string& host_id, const std::string& transmission_id) {
   std::lock_guard<std::recursive_mutex> lock(ws_hdl_alive_checker_mutex_);
diff --git a/src/transmission_manager.h b/src/transmission_manager.h
index fde9645..11795b9 100644
--- a/src/transmission_manager.h
+++ b/src/transmission_manager.h
@@ -30,6 +30,8 @@ class TransmissionManager {
   std::vector<std::string> GetAllUserIdOfTransmission(
       const std::string& transmission_id);
 
+  std::string GetHostIdOfTransmission(const std::string& transmission_id);
+
   bool BindHostToTransmission(const std::string& host_id,
                               const std::string& transmission_id);
   bool BindGuestToTransmission(const std::string& guest_id,