BaseTcpConnection

UBaseTcpConnection defines a shared foundation for handling TCP connections between Unreal Engine and external Python clients. It is used as a superclass for specialized implementations like USingleTcpConnection, and provides support for listening sockets, message transmission, handshake management, and connection delegation.

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Overview

This class listens for incoming TCP connections and assigns the first to the "admin" role, with subsequent sockets handled by child implementations. It abstracts message send/receive logic and exposes a common interface for socket-based interaction.

Admin socket acts as a control interface for the python module to manage the training process.

It does not start threads on its own, but is intended to integrate cleanly with threaded accept loops.

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Connection Lifecycle

bool StartListening(const FString& IPAddress, int32 Port) (pure virtual)

To be implemented by subclasses. Should bind a listening socket to the specified IP/Port and optionally start an acceptance thread.

bool AcceptConnection()

Accepts a pending connection from the listening socket.

• First connection becomes the admin socket.
• Additional connections are routed to AcceptEnvConnection().
• Returns true on success; logs and returns false on failure.

virtual bool AcceptEnvConnection(FSocket* InNewSocket) (pure virtual)

Must be implemented by subclasses. Defines what to do with environment connections.

virtual void CloseConnection() (pure virtual)

Shuts down any listening sockets, threads, and client sockets.

FSocket* GetListeningSocket()

Returns the active listening socket pointer. Used in threaded polling or external socket validation.

virtual void StartAcceptThread() (pure virtual)

To be implemented by subclasses. Launches a background thread that polls ListeningSocket and calls AcceptConnection() when a client connects.

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Messaging API

bool SendMessageAdmin(const FString& Data)

Sends a UTF-8 message to the admin socket. Logs failure and returns false if the socket is unavailable.

FString ReceiveMessageAdmin(int32 BufSize = 1024)

Receives a UTF-8 string from the admin socket, if data is available. Returns an empty string otherwise.

virtual bool SendMessageEnv(const FString& Data) (pure virtual)

Subclasses must define how to send data to the environment connection(s).

virtual FString ReceiveMessageEnv(int32 BufSize = 1024) (pure virtual)

Subclasses must define how to receive data from environment socket(s).

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Handshake

void SetHandshake(const FString& InHandshakeMsg)

Stores a string to be sent to the admin socket after a successful connection.

void SendHandshake()

Immediately sends the stored handshake string to the admin socket.

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Internal State & Members

• FSocket* ListeningSocket — The TCP server socket accepting incoming connections.
• FSocket* AdminSocket — The first client that connects; reserved for handshake/config.
• FString HandshakeMessage — Stored handshake configuration string.
• FRunnableThread* AcceptThreadRef — Optional background thread for socket polling (managed by subclasses).
• TSharedPtr<FAcceptRunnable> — Threaded runnable used in USingleTcpConnection to poll for connections.
• bool bStopAcceptThreadRef — Flag shared with thread to trigger shutdown.

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Logging

UBaseTcpConnection logs all major events, including:

• Socket binding success/failure
• Connection acceptance
• Message transmission
• Read/write errors

This aids in debugging both bridge-side and Python-side communication.

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