Kernel/IPC: Use Ports and Sessions as the fundamental building block of Inter Process Communication.

All handles obtained via srv::GetServiceHandle or svcConnectToPort are references to ClientSessions.
Service modules will wait on the counterpart of those ClientSessions (Called ServerSessions) using svcReplyAndReceive or svcWaitSynchronization[1|N], and will be awoken when a SyncRequest is performed.

HLE Interfaces are now ClientPorts which override the HandleSyncRequest virtual member function to perform command handling immediately.

16 files changed, 314 insertions, 88 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 299f1f261..59260d2e8 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -36,6 +36,7 @@ set(SRCS
             hle/applets/swkbd.cpp
             hle/kernel/address_arbiter.cpp
             hle/kernel/client_port.cpp
+            hle/kernel/client_session.cpp
             hle/kernel/event.cpp
             hle/kernel/kernel.cpp
             hle/kernel/memory.cpp
@@ -44,7 +45,7 @@ set(SRCS
             hle/kernel/resource_limit.cpp
             hle/kernel/semaphore.cpp
             hle/kernel/server_port.cpp
-            hle/kernel/session.cpp
+            hle/kernel/server_session.cpp
             hle/kernel/shared_memory.cpp
             hle/kernel/thread.cpp
             hle/kernel/timer.cpp
@@ -184,6 +185,7 @@ set(HEADERS
             hle/applets/swkbd.h
             hle/kernel/address_arbiter.h
             hle/kernel/client_port.h
+            hle/kernel/client_session.h
             hle/kernel/event.h
             hle/kernel/kernel.h
             hle/kernel/memory.h
@@ -192,7 +194,7 @@ set(HEADERS
             hle/kernel/resource_limit.h
             hle/kernel/semaphore.h
             hle/kernel/server_port.h
-            hle/kernel/session.h
+            hle/kernel/server_session.h
             hle/kernel/shared_memory.h
             hle/kernel/thread.h
             hle/kernel/timer.h
diff --git a/src/core/hle/kernel/client_port.cpp b/src/core/hle/kernel/client_port.cpp
index aedc6f989..5ee7679eb 100644
--- a/src/core/hle/kernel/client_port.cpp
+++ b/src/core/hle/kernel/client_port.cpp
@@ -6,10 +6,17 @@
 #include "core/hle/kernel/client_port.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/server_port.h"
+#include "core/hle/kernel/server_session.h"
 
 namespace Kernel {
 
 ClientPort::ClientPort() {}
 ClientPort::~ClientPort() {}
 
+void ClientPort::AddWaitingSession(SharedPtr<ServerSession> server_session) {
+    server_port->pending_sessions.push_back(server_session);
+    // Wake the threads waiting on the ServerPort
+    server_port->WakeupAllWaitingThreads();
+}
+
 } // namespace
diff --git a/src/core/hle/kernel/client_port.h b/src/core/hle/kernel/client_port.h
index d28147718..eb0882870 100644
--- a/src/core/hle/kernel/client_port.h
+++ b/src/core/hle/kernel/client_port.h
@@ -11,16 +11,27 @@
 namespace Kernel {
 
 class ServerPort;
+class ServerSession;
 
 class ClientPort : public Object {
 public:
     friend class ServerPort;
-    std::string GetTypeName() const override {
-        return "ClientPort";
-    }
-    std::string GetName() const override {
-        return name;
-    }
+
+    /**
+     * Adds the specified server session to the queue of pending sessions of the associated ServerPort
+     * @param server_session Server session to add to the queue
+     */
+    virtual void AddWaitingSession(SharedPtr<ServerSession> server_session);
+
+    /**
+     * Handle a sync request from the emulated application.
+     * Only HLE services should override this function.
+     * @returns ResultCode from the operation.
+     */
+    virtual ResultCode HandleSyncRequest() { return RESULT_SUCCESS; }
+
+    std::string GetTypeName() const override { return "ClientPort"; }
+    std::string GetName() const override { return name; }
 
     static const HandleType HANDLE_TYPE = HandleType::ClientPort;
     HandleType GetHandleType() const override {
diff --git a/src/core/hle/kernel/client_session.cpp b/src/core/hle/kernel/client_session.cpp
new file mode 100644
index 000000000..f1ad9b65b
--- /dev/null
+++ b/src/core/hle/kernel/client_session.cpp
@@ -0,0 +1,42 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/assert.h"
+
+#include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/client_session.h"
+#include "core/hle/kernel/server_session.h"
+#include "core/hle/kernel/kernel.h"
+
+namespace Kernel {
+
+ClientSession::ClientSession() {}
+ClientSession::~ClientSession() {}
+
+ResultVal<SharedPtr<ClientSession>> ClientSession::Create(SharedPtr<ServerSession> server_session, SharedPtr<ClientPort> client_port, std::string name) {
+    SharedPtr<ClientSession> client_session(new ClientSession);
+
+    client_session->name = std::move(name);
+    client_session->server_session = server_session;
+    client_session->client_port = client_port;
+
+    return MakeResult<SharedPtr<ClientSession>>(std::move(client_session));
+}
+
+ResultCode ClientSession::HandleSyncRequest() {
+    // Signal the server session that new data is available
+    ResultCode result = server_session->HandleSyncRequest();
+
+    if (result.IsError())
+        return result;
+
+    // Tell the client port to handle the request in case it's an HLE service.
+    // The client port can be nullptr for port-less sessions (Like for example File and Directory sessions).
+    if (client_port != nullptr)
+        result = client_port->HandleSyncRequest();
+
+    return result;
+}
+
+} // namespace
diff --git a/src/core/hle/kernel/client_session.h b/src/core/hle/kernel/client_session.h
new file mode 100644
index 000000000..4fe9b4517
--- /dev/null
+++ b/src/core/hle/kernel/client_session.h
@@ -0,0 +1,50 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+
+#include "common/common_types.h"
+
+#include "core/hle/kernel/kernel.h"
+
+namespace Kernel {
+
+class ClientPort;
+class ServerSession;
+
+class ClientSession final : public Object {
+public:
+    /**
+     * Creates a client session.
+     * @param server_session The server session associated with this client session
+     * @param client_port The client port which this session is connected to
+     * @param name Optional name of client session
+     * @return The created client session
+     */
+    static ResultVal<SharedPtr<ClientSession>> Create(SharedPtr<ServerSession> server_session, SharedPtr<ClientPort> client_port, std::string name = "Unknown");
+
+    std::string GetTypeName() const override { return "ClientSession"; }
+    std::string GetName() const override { return name; }
+
+    static const HandleType HANDLE_TYPE = HandleType::ClientSession;
+    HandleType GetHandleType() const override { return HANDLE_TYPE; }
+
+    /**
+     * Handle a SyncRequest from the emulated application.
+     * @return ResultCode of the operation.
+     */
+    ResultCode HandleSyncRequest();
+
+    std::string name;                           ///< Name of client port (optional)
+    SharedPtr<ServerSession> server_session;    ///< The server session associated with this client session.
+    SharedPtr<ClientPort> client_port;          ///< The client port which this session is connected to.
+
+private:
+    ClientSession();
+    ~ClientSession() override;
+};
+
+} // namespace
diff --git a/src/core/hle/kernel/kernel.h b/src/core/hle/kernel/kernel.h
index 231cf7b75..c11c14b7d 100644
--- a/src/core/hle/kernel/kernel.h
+++ b/src/core/hle/kernel/kernel.h
@@ -31,22 +31,24 @@ enum KernelHandle : Handle {
 };
 
 enum class HandleType : u32 {
-    Unknown = 0,
-
-    Session = 2,
-    Event = 3,
-    Mutex = 4,
-    SharedMemory = 5,
-    Redirection = 6,
-    Thread = 7,
-    Process = 8,
-    AddressArbiter = 9,
-    Semaphore = 10,
-    Timer = 11,
-    ResourceLimit = 12,
-    CodeSet = 13,
-    ClientPort = 14,
-    ServerPort = 15,
+    Unknown         = 0,
+
+
+    Event           = 3,
+    Mutex           = 4,
+    SharedMemory    = 5,
+    Redirection     = 6,
+    Thread          = 7,
+    Process         = 8,
+    AddressArbiter  = 9,
+    Semaphore       = 10,
+    Timer           = 11,
+    ResourceLimit   = 12,
+    CodeSet         = 13,
+    ClientPort      = 14,
+    ServerPort      = 15,
+    ClientSession   = 16,
+    ServerSession   = 17,
 };
 
 enum {
@@ -82,7 +84,7 @@ public:
      */
     bool IsWaitable() const {
         switch (GetHandleType()) {
-        case HandleType::Session:
+        case HandleType::ServerSession:
         case HandleType::ServerPort:
         case HandleType::Event:
         case HandleType::Mutex:
diff --git a/src/core/hle/kernel/server_session.cpp b/src/core/hle/kernel/server_session.cpp
new file mode 100644
index 000000000..9f5350ce5
--- /dev/null
+++ b/src/core/hle/kernel/server_session.cpp
@@ -0,0 +1,58 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <tuple>
+
+#include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/client_session.h"
+#include "core/hle/kernel/server_session.h"
+#include "core/hle/kernel/thread.h"
+
+namespace Kernel {
+
+ServerSession::ServerSession() {}
+ServerSession::~ServerSession() {}
+
+ResultVal<SharedPtr<ServerSession>> ServerSession::Create(std::string name) {
+    SharedPtr<ServerSession> server_session(new ServerSession);
+
+    server_session->name = std::move(name);
+    server_session->signaled = false;
+
+    return MakeResult<SharedPtr<ServerSession>>(std::move(server_session));
+}
+
+bool ServerSession::ShouldWait() {
+    return !signaled;
+}
+
+void ServerSession::Acquire() {
+    ASSERT_MSG(!ShouldWait(), "object unavailable!");
+    signaled = false;
+}
+
+ResultCode ServerSession::HandleSyncRequest() {
+    // The ServerSession received a sync request, this means that there's new data available
+    // from one of its ClientSessions, so wake up any threads that may be waiting on a svcReplyAndReceive or similar.
+    signaled = true;
+    WakeupAllWaitingThreads();
+    return RESULT_SUCCESS;
+}
+
+SharedPtr<ClientSession> ServerSession::CreateClientSession() {
+    // In Citra, some types of ServerSessions (File and Directory sessions) are not created as a pair of Server-Client sessions,
+    // but are instead created as a single ServerSession, which then hands over a ClientSession on demand (When opening the File or Directory).
+    // The real kernel (Or more specifically, the real FS service) does create the pair of Sessions at the same time (via svcCreateSession), and simply
+    // stores the ClientSession until it is needed.
+    return ClientSession::Create(SharedPtr<ServerSession>(this), nullptr, name + "Client").MoveFrom();
+}
+
+std::tuple<SharedPtr<ServerSession>, SharedPtr<ClientSession>> ServerSession::CreateSessionPair(SharedPtr<ClientPort> client_port, std::string name) {
+    auto server_session = ServerSession::Create(name + "Server").MoveFrom();
+    auto client_session = ClientSession::Create(server_session, client_port, name + "Client").MoveFrom();
+
+    return std::make_tuple(server_session, client_session);
+}
+
+}
diff --git a/src/core/hle/kernel/session.h b/src/core/hle/kernel/server_session.h
index ec025f732..eab9fe211 100644
--- a/src/core/hle/kernel/session.h
+++ b/src/core/hle/kernel/server_session.h
@@ -162,57 +162,64 @@ inline u32* GetCommandBuffer(const int offset = 0) {
                                     offset);
 }
 
+class ClientSession;
+class ClientPort;
+
 /**
- * Kernel object representing the client endpoint of an IPC session. Sessions are the basic CTR-OS
+ * Kernel object representing the server endpoint of an IPC session. Sessions are the basic CTR-OS
  * primitive for communication between different processes, and are used to implement service calls
  * to the various system services.
  *
  * To make a service call, the client must write the command header and parameters to the buffer
  * located at offset 0x80 of the TLS (Thread-Local Storage) area, then execute a SendSyncRequest
- * SVC call with its Session handle. The kernel will read the command header, using it to marshall
+ * SVC call with its ClientSession handle. The kernel will read the command header, using it to marshall
  * the parameters to the process at the server endpoint of the session. After the server replies to
  * the request, the response is marshalled back to the caller's TLS buffer and control is
  * transferred back to it.
- *
- * In Citra, only the client endpoint is currently implemented and only HLE calls, where the IPC
- * request is answered by C++ code in the emulator, are supported. When SendSyncRequest is called
- * with the session handle, this class's SyncRequest method is called, which should read the TLS
- * buffer and emulate the call accordingly. Since the code can directly read the emulated memory,
- * no parameter marshalling is done.
- *
- * In the long term, this should be turned into the full-fledged IPC mechanism implemented by
- * CTR-OS so that IPC calls can be optionally handled by the real implementations of processes, as
- * opposed to HLE simulations.
  */
-class Session : public WaitObject {
+class ServerSession : public WaitObject {
 public:
-    Session();
-    ~Session() override;
+    ServerSession();
+    ~ServerSession() override;
+
+    /**
+     * Creates a server session.
+     * @param name Optional name of the server session
+     * @return The created server session
+     */
+    static ResultVal<SharedPtr<ServerSession>> Create(std::string name = "Unknown");
 
-    std::string GetTypeName() const override {
-        return "Session";
-    }
+    std::string GetTypeName() const override { return "ServerSession"; }
 
-    static const HandleType HANDLE_TYPE = HandleType::Session;
-    HandleType GetHandleType() const override {
-        return HANDLE_TYPE;
-    }
+    static const HandleType HANDLE_TYPE = HandleType::ServerSession;
+    HandleType GetHandleType() const override { return HANDLE_TYPE; }
+
+    /**
+     * Creates a pair of ServerSession and an associated ClientSession.
+     * @param client_port ClientPort to which the sessions are connected
+     * @param name Optional name of the ports
+     * @return The created session tuple
+     */
+    static std::tuple<SharedPtr<ServerSession>, SharedPtr<ClientSession>> CreateSessionPair(SharedPtr<ClientPort> client_port, std::string name = "Unknown");
+
+    /**
+     * Creates a portless ClientSession and associates it with this ServerSession.
+     * @returns ClientSession The newly created ClientSession.
+     */
+    SharedPtr<ClientSession> CreateClientSession();
 
     /**
-     * Handles a synchronous call to this session using HLE emulation. Emulated <-> emulated calls
-     * aren't supported yet.
+     * Handle a sync request from the emulated application.
+     * Only HLE services should override this function.
+     * @returns ResultCode from the operation.
      */
-    virtual ResultVal<bool> SyncRequest() = 0;
+    virtual ResultCode HandleSyncRequest();
 
-    // TODO(bunnei): These functions exist to satisfy a hardware test with a Session object
-    // passed into WaitSynchronization. Figure out the meaning of them.
+    bool ShouldWait() override;
 
-    bool ShouldWait() override {
-        return true;
-    }
+    void Acquire() override;
 
-    void Acquire() override {
-        ASSERT_MSG(!ShouldWait(), "object unavailable!");
-    }
+    std::string name; ///< The name of this session (optional)
+    bool signaled;    ///< Whether there's new data available to this ServerSession
 };
 }
diff --git a/src/core/hle/service/fs/archive.cpp b/src/core/hle/service/fs/archive.cpp
index 4c29784e8..da009df91 100644
--- a/src/core/hle/service/fs/archive.cpp
+++ b/src/core/hle/service/fs/archive.cpp
@@ -92,7 +92,7 @@ File::File(std::unique_ptr<FileSys::FileBackend>&& backend, const FileSys::Path&
 
 File::~File() {}
 
-ResultVal<bool> File::SyncRequest() {
+ResultCode File::HandleSyncRequest() {
     u32* cmd_buff = Kernel::GetCommandBuffer();
     FileCommand cmd = static_cast<FileCommand>(cmd_buff[0]);
     switch (cmd) {
@@ -193,10 +193,10 @@ ResultVal<bool> File::SyncRequest() {
         LOG_ERROR(Service_FS, "Unknown command=0x%08X!", cmd);
         ResultCode error = UnimplementedFunction(ErrorModule::FS);
         cmd_buff[1] = error.raw; // TODO(Link Mauve): use the correct error code for that.
-        return error;
+        return ServerSession::HandleSyncRequest();
     }
     cmd_buff[1] = RESULT_SUCCESS.raw; // No error
-    return MakeResult<bool>(false);
+    return ServerSession::HandleSyncRequest();
 }
 
 Directory::Directory(std::unique_ptr<FileSys::DirectoryBackend>&& backend,
@@ -205,7 +205,7 @@ Directory::Directory(std::unique_ptr<FileSys::DirectoryBackend>&& backend,
 
 Directory::~Directory() {}
 
-ResultVal<bool> Directory::SyncRequest() {
+ResultCode Directory::HandleSyncRequest() {
     u32* cmd_buff = Kernel::GetCommandBuffer();
     DirectoryCommand cmd = static_cast<DirectoryCommand>(cmd_buff[0]);
     switch (cmd) {
@@ -236,10 +236,10 @@ ResultVal<bool> Directory::SyncRequest() {
         LOG_ERROR(Service_FS, "Unknown command=0x%08X!", cmd);
         ResultCode error = UnimplementedFunction(ErrorModule::FS);
         cmd_buff[1] = error.raw; // TODO(Link Mauve): use the correct error code for that.
-        return MakeResult<bool>(false);
+        return ServerSession::HandleSyncRequest();
     }
     cmd_buff[1] = RESULT_SUCCESS.raw; // No error
-    return MakeResult<bool>(false);
+    return ServerSession::HandleSyncRequest();
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/src/core/hle/service/fs/archive.h b/src/core/hle/service/fs/archive.h
index 21ed9717b..22e659c40 100644
--- a/src/core/hle/service/fs/archive.h
+++ b/src/core/hle/service/fs/archive.h
@@ -8,7 +8,7 @@
 #include <string>
 #include "common/common_types.h"
 #include "core/file_sys/archive_backend.h"
-#include "core/hle/kernel/session.h"
+#include "core/hle/kernel/server_session.h"
 #include "core/hle/result.h"
 
 namespace FileSys {
@@ -41,7 +41,7 @@ enum class MediaType : u32 { NAND = 0, SDMC = 1 };
 
 typedef u64 ArchiveHandle;
 
-class File : public Kernel::Session {
+class File : public Kernel::ServerSession {
 public:
     File(std::unique_ptr<FileSys::FileBackend>&& backend, const FileSys::Path& path);
     ~File();
@@ -49,14 +49,15 @@ public:
     std::string GetName() const override {
         return "Path: " + path.DebugStr();
     }
-    ResultVal<bool> SyncRequest() override;
+
+    ResultCode HandleSyncRequest() override;
 
     FileSys::Path path; ///< Path of the file
     u32 priority;       ///< Priority of the file. TODO(Subv): Find out what this means
     std::unique_ptr<FileSys::FileBackend> backend; ///< File backend interface
 };
 
-class Directory : public Kernel::Session {
+class Directory : public Kernel::ServerSession {
 public:
     Directory(std::unique_ptr<FileSys::DirectoryBackend>&& backend, const FileSys::Path& path);
     ~Directory();
@@ -64,7 +65,8 @@ public:
     std::string GetName() const override {
         return "Directory: " + path.DebugStr();
     }
-    ResultVal<bool> SyncRequest() override;
+
+    ResultCode HandleSyncRequest() override;
 
     FileSys::Path path;                                 ///< Path of the directory
     std::unique_ptr<FileSys::DirectoryBackend> backend; ///< File backend interface
diff --git a/src/core/hle/service/fs/fs_user.cpp b/src/core/hle/service/fs/fs_user.cpp
index 9ec17b395..bb78091f9 100644
--- a/src/core/hle/service/fs/fs_user.cpp
+++ b/src/core/hle/service/fs/fs_user.cpp
@@ -8,6 +8,7 @@
 #include "common/logging/log.h"
 #include "common/scope_exit.h"
 #include "common/string_util.h"
+#include "core/hle/kernel/client_session.h"
 #include "core/hle/result.h"
 #include "core/hle/service/fs/archive.h"
 #include "core/hle/service/fs/fs_user.h"
@@ -17,7 +18,7 @@
 // Namespace FS_User
 
 using Kernel::SharedPtr;
-using Kernel::Session;
+using Kernel::ServerSession;
 
 namespace Service {
 namespace FS {
@@ -70,7 +71,7 @@ static void OpenFile(Service::Interface* self) {
     ResultVal<SharedPtr<File>> file_res = OpenFileFromArchive(archive_handle, file_path, mode);
     cmd_buff[1] = file_res.Code().raw;
     if (file_res.Succeeded()) {
-        cmd_buff[3] = Kernel::g_handle_table.Create(*file_res).MoveFrom();
+        cmd_buff[3] = Kernel::g_handle_table.Create((*file_res)->CreateClientSession()).MoveFrom();
     } else {
         cmd_buff[3] = 0;
         LOG_ERROR(Service_FS, "failed to get a handle for file %s", file_path.DebugStr().c_str());
@@ -130,7 +131,7 @@ static void OpenFileDirectly(Service::Interface* self) {
     ResultVal<SharedPtr<File>> file_res = OpenFileFromArchive(*archive_handle, file_path, mode);
     cmd_buff[1] = file_res.Code().raw;
     if (file_res.Succeeded()) {
-        cmd_buff[3] = Kernel::g_handle_table.Create(*file_res).MoveFrom();
+        cmd_buff[3] = Kernel::g_handle_table.Create((*file_res)->CreateClientSession()).MoveFrom();
     } else {
         cmd_buff[3] = 0;
         LOG_ERROR(Service_FS, "failed to get a handle for file %s mode=%u attributes=%u",
@@ -391,7 +392,7 @@ static void OpenDirectory(Service::Interface* self) {
     ResultVal<SharedPtr<Directory>> dir_res = OpenDirectoryFromArchive(archive_handle, dir_path);
     cmd_buff[1] = dir_res.Code().raw;
     if (dir_res.Succeeded()) {
-        cmd_buff[3] = Kernel::g_handle_table.Create(*dir_res).MoveFrom();
+        cmd_buff[3] = Kernel::g_handle_table.Create((*dir_res)->CreateClientSession()).MoveFrom();
     } else {
         LOG_ERROR(Service_FS, "failed to get a handle for directory type=%d size=%d data=%s",
                   dirname_type, dirname_size, dir_path.DebugStr().c_str());
diff --git a/src/core/hle/service/service.cpp b/src/core/hle/service/service.cpp
index ca7eeac8a..f51a042ff 100644
--- a/src/core/hle/service/service.cpp
+++ b/src/core/hle/service/service.cpp
@@ -41,8 +41,8 @@
 
 namespace Service {
 
-std::unordered_map<std::string, Kernel::SharedPtr<Interface>> g_kernel_named_ports;
-std::unordered_map<std::string, Kernel::SharedPtr<Interface>> g_srv_services;
+std::unordered_map<std::string, Kernel::SharedPtr<Kernel::ClientPort>> g_kernel_named_ports;
+std::unordered_map<std::string, Kernel::SharedPtr<Kernel::ClientPort>> g_srv_services;
 
 /**
  * Creates a function string for logging, complete with the name (or header code, depending
@@ -61,7 +61,7 @@ static std::string MakeFunctionString(const char* name, const char* port_name,
     return function_string;
 }
 
-ResultVal<bool> Interface::SyncRequest() {
+ResultCode Interface::HandleSyncRequest() {
     u32* cmd_buff = Kernel::GetCommandBuffer();
     auto itr = m_functions.find(cmd_buff[0]);
 
@@ -75,14 +75,14 @@ ResultVal<bool> Interface::SyncRequest() {
 
         // TODO(bunnei): Hack - ignore error
         cmd_buff[1] = 0;
-        return MakeResult<bool>(false);
+        return RESULT_SUCCESS;
     }
     LOG_TRACE(Service, "%s",
               MakeFunctionString(itr->second.name, GetPortName().c_str(), cmd_buff).c_str());
 
     itr->second.func(this);
 
-    return MakeResult<bool>(false); // TODO: Implement return from actual function
+    return RESULT_SUCCESS; // TODO: Implement return from actual function, it should fail if the parameter translation fails
 }
 
 void Interface::Register(const FunctionInfo* functions, size_t n) {
@@ -97,10 +97,16 @@ void Interface::Register(const FunctionInfo* functions, size_t n) {
 // Module interface
 
 static void AddNamedPort(Interface* interface_) {
+    interface_->name = interface_->GetPortName();
+    interface_->active_sessions = 0;
+    interface_->max_sessions = interface_->GetMaxSessions();
     g_kernel_named_ports.emplace(interface_->GetPortName(), interface_);
 }
 
 void AddService(Interface* interface_) {
+    interface_->name = interface_->GetPortName();
+    interface_->active_sessions = 0;
+    interface_->max_sessions = interface_->GetMaxSessions();
     g_srv_services.emplace(interface_->GetPortName(), interface_);
 }
 
diff --git a/src/core/hle/service/service.h b/src/core/hle/service/service.h
index 29daacfc4..fd15ad03f 100644
--- a/src/core/hle/service/service.h
+++ b/src/core/hle/service/service.h
@@ -9,7 +9,8 @@
 #include <unordered_map>
 #include <boost/container/flat_map.hpp>
 #include "common/common_types.h"
-#include "core/hle/kernel/session.h"
+#include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/server_session.h"
 #include "core/hle/result.h"
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -18,9 +19,10 @@
 namespace Service {
 
 static const int kMaxPortSize = 8; ///< Maximum size of a port name (8 characters)
+static const u32 DefaultMaxSessions = 10; ///< Arbitrary default number of maximum connections to an HLE port
 
 /// Interface to a CTROS service
-class Interface : public Kernel::Session {
+class Interface : public Kernel::ClientPort {
     // TODO(yuriks): An "Interface" being a Kernel::Object is mostly non-sense. Interface should be
     // just something that encapsulates a session and acts as a helper to implement service
     // processes.
@@ -33,6 +35,15 @@ public:
         version.raw = raw_version;
     }
 
+    /**
+     * Gets the maximum allowed number of sessions that can be connected to this port at the same time.
+     * It should be overwritten by each service implementation for more fine-grained control.
+     * @returns The maximum number of connections allowed.
+     */
+    virtual u32 GetMaxSessions() { return DefaultMaxSessions; }
+
+    void AddWaitingSession(Kernel::SharedPtr<Kernel::ServerSession> server_session) override { }
+
     typedef void (*Function)(Interface*);
 
     struct FunctionInfo {
@@ -49,7 +60,7 @@ public:
         return "[UNKNOWN SERVICE PORT]";
     }
 
-    ResultVal<bool> SyncRequest() override;
+    ResultCode HandleSyncRequest() override;
 
 protected:
     /**
@@ -81,9 +92,9 @@ void Init();
 void Shutdown();
 
 /// Map of named ports managed by the kernel, which can be retrieved using the ConnectToPort SVC.
-extern std::unordered_map<std::string, Kernel::SharedPtr<Interface>> g_kernel_named_ports;
+extern std::unordered_map<std::string, Kernel::SharedPtr<Kernel::ClientPort>> g_kernel_named_ports;
 /// Map of services registered with the "srv:" service, retrieved using GetServiceHandle.
-extern std::unordered_map<std::string, Kernel::SharedPtr<Interface>> g_srv_services;
+extern std::unordered_map<std::string, Kernel::SharedPtr<Kernel::ClientPort>> g_srv_services;
 
 /// Adds a service to the services table
 void AddService(Interface* interface_);
diff --git a/src/core/hle/service/soc_u.cpp b/src/core/hle/service/soc_u.cpp
index 46b75db25..2e8b2fc00 100644
--- a/src/core/hle/service/soc_u.cpp
+++ b/src/core/hle/service/soc_u.cpp
@@ -11,7 +11,7 @@
 #include "common/common_types.h"
 #include "common/logging/log.h"
 #include "common/scope_exit.h"
-#include "core/hle/kernel/session.h"
+#include "core/hle/kernel/server_session.h"
 #include "core/hle/result.h"
 #include "core/hle/service/soc_u.h"
 #include "core/memory.h"
diff --git a/src/core/hle/service/srv.cpp b/src/core/hle/service/srv.cpp
index b25be413a..eb2e06041 100644
--- a/src/core/hle/service/srv.cpp
+++ b/src/core/hle/service/srv.cpp
@@ -2,8 +2,12 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <tuple>
+
 #include "common/common_types.h"
 #include "common/logging/log.h"
+#include "core/hle/service/srv.h"
+#include "core/hle/kernel/client_session.h"
 #include "core/hle/kernel/event.h"
 #include "core/hle/service/srv.h"
 
@@ -81,7 +85,18 @@ static void GetServiceHandle(Service::Interface* self) {
     auto it = Service::g_srv_services.find(port_name);
 
     if (it != Service::g_srv_services.end()) {
-        cmd_buff[3] = Kernel::g_handle_table.Create(it->second).MoveFrom();
+        auto client_port = it->second;
+
+        // Create a new session pair
+        auto sessions = Kernel::ServerSession::CreateSessionPair(client_port, port_name);
+        auto client_session = std::get<Kernel::SharedPtr<Kernel::ClientSession>>(sessions);
+        auto server_session = std::get<Kernel::SharedPtr<Kernel::ServerSession>>(sessions);
+
+        // Add the server session to the port's queue
+        client_port->AddWaitingSession(server_session);
+
+        // Return the client session
+        cmd_buff[3] = Kernel::g_handle_table.Create(client_session).MoveFrom();
         LOG_TRACE(Service_SRV, "called port=%s, handle=0x%08X", port_name.c_str(), cmd_buff[3]);
     } else {
         LOG_ERROR(Service_SRV, "(UNIMPLEMENTED) called port=%s", port_name.c_str());
diff --git a/src/core/hle/svc.cpp b/src/core/hle/svc.cpp
index c6b80dc50..be03e53bc 100644
--- a/src/core/hle/svc.cpp
+++ b/src/core/hle/svc.cpp
@@ -13,6 +13,7 @@
 #include "core/hle/function_wrappers.h"
 #include "core/hle/kernel/address_arbiter.h"
 #include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/client_session.h"
 #include "core/hle/kernel/event.h"
 #include "core/hle/kernel/memory.h"
 #include "core/hle/kernel/mutex.h"
@@ -222,20 +223,31 @@ static ResultCode ConnectToPort(Handle* out_handle, const char* port_name) {
         return ERR_NOT_FOUND;
     }
 
-    CASCADE_RESULT(*out_handle, Kernel::g_handle_table.Create(it->second));
+    auto client_port = it->second;
+
+    // Create a new session pair
+    auto sessions = Kernel::ServerSession::CreateSessionPair(client_port, port_name);
+    auto client_session = std::get<Kernel::SharedPtr<Kernel::ClientSession>>(sessions);
+    auto server_session = std::get<Kernel::SharedPtr<Kernel::ServerSession>>(sessions);
+
+    // Add the server session to the port's queue
+    client_port->AddWaitingSession(server_session);
+
+    // Return the client session
+    CASCADE_RESULT(*out_handle, Kernel::g_handle_table.Create(client_session));
     return RESULT_SUCCESS;
 }
 
 /// Synchronize to an OS service
 static ResultCode SendSyncRequest(Handle handle) {
-    SharedPtr<Kernel::Session> session = Kernel::g_handle_table.Get<Kernel::Session>(handle);
+    SharedPtr<Kernel::ClientSession> session = Kernel::g_handle_table.Get<Kernel::ClientSession>(handle);
     if (session == nullptr) {
         return ERR_INVALID_HANDLE;
     }
 
     LOG_TRACE(Kernel_SVC, "called handle=0x%08X(%s)", handle, session->GetName().c_str());
 
-    return session->SyncRequest().Code();
+    return session->HandleSyncRequest();
 }
 
 /// Close a handle