Return an error code when connecting to a saturated port.

The error code was taken from the 3DS kernel.

src/core/hle/kernel/client_port.cpp

@@ -14,7 +14,14 @@ namespace Kernel {
 ClientPort::ClientPort() {}
 ClientPort::~ClientPort() {}
 
-SharedPtr<ClientSession> ClientPort::Connect() {
+ResultVal<SharedPtr<ClientSession>> ClientPort::Connect() {
+    if (active_sessions >= max_sessions) {
+        return ResultCode(ErrorDescription::MaxConnectionsReached,
+                          ErrorModule::OS, ErrorSummary::WouldBlock,
+                          ErrorLevel::Temporary);
+    }
+    active_sessions++;
+
     // Create a new session pair, let the created sessions inherit the parent port's HLE handler.
     auto sessions = ServerSession::CreateSessionPair(server_port->GetName(), server_port->hle_handler);
     auto client_session = std::get<SharedPtr<ClientSession>>(sessions);
@@ -25,7 +32,7 @@ SharedPtr<ClientSession> ClientPort::Connect() {
     // Wake the threads waiting on the ServerPort
     server_port->WakeupAllWaitingThreads();
 
-    return std::move(client_session);
+    return MakeResult<SharedPtr<ClientSession>>(std::move(client_session));
 }
 
 } // namespace

src/core/hle/kernel/client_port.h

@@ -31,9 +31,9 @@ public:
     /**
      * Creates a new Session pair, adds the created ServerSession to the associated ServerPort's list of pending sessions,
      * and signals the ServerPort, causing any threads waiting on it to awake.
-     * @returns ClientSession The client endpoint of the created Session pair.
+     * @returns ClientSession The client endpoint of the created Session pair, or error code.
      */
-    SharedPtr<ClientSession> Connect();
+    ResultVal<SharedPtr<ClientSession>> Connect();
 
     SharedPtr<ServerPort> server_port; ///< ServerPort associated with this client port.
     u32 max_sessions;    ///< Maximum number of simultaneous sessions the port can have