Cpp-SocketLibrary

A ServerSocket and Socket library for Windows and Linux aiming to support both Wifi and Bluetooth communication.

Getting Started

Dependencies

• CMake and make

The following linux dependencies are required:

• libbluetooth-dev
• libglib2.0-dev
• bluez

Building the Library and Running the Tests - Linux

1. To build the library, firstly run cmake: cmake . -B build-linux in the root directory of the repository (CppSocketLibrary/).
2. Then move into the new build-linux folder: cd build-linux.
3. Then you can run make to build the library.
4. Then you can run make check to run the available tests.

Building the Library and Running the Tests - Windows

1. To build the library, firstly run cmake: cmake . -B build in the root directory of the repository (CppSocketLibrary/).
2. This will create a .sln file which can be opened in Visual Studio.
3. Once opened (and with the appropriate windows service packs installed - MSVC v143 - VS 2022 C++ x64/x86 Spectre-mitigated libs (v14.29-16.11))
4. You can then build and run the CppSocketLibraryTest project and it will rebuild the library and run the appropriate tests.

Usage Examples

• TCP Example using IPV6:

void tcpExample()
{
    // Create a new Wifi ServerSocket
    kt::ServerSocket server(kt::SocketType::Wifi, 56756, 20, kt::InternetProtocolVersion::IPV6);

    // Create new TCP socket
    kt::TCPSocket client("::1", server.getPort());

    // Accept the incoming connection at the server
    kt::TCPSocket serverSocket = server.acceptTCPConnection();

    // Send string with text before and after the delimiter
    const std::string testString = "TCP Delimiter Test";
    const char delimiter = '~';
    if (!client.send(testString + delimiter + "other string").first)
    {
        std::cout << "Failed to send test string" << std::endl;
        return;
    }

    if (serverSocket.ready())
    {
        std::string response = serverSocket.receiveToDelimiter(delimiter);
        // Check that the received string is the same as the string sent by the client
        ASSERT_EQ(response, testString);
    }

    // Close all sockets
    client.close();
    serverSocket.close();
    server.close();
}

• UDP Example using IPV4 (the default protocol version - so protocol related arguments are omitted):

void udpExample() 
{
    // The socket receiving data must first be bound
    kt::UDPSocket socket;
    socket.bind(37893, kt::InternetProtocolVersion::IPV4);

    kt::UDPSocket client;
    const std::string testString = "UDP test string";
    if (!client.sendTo("localhost", 37893, testString).first.first)
    {
        std::cout << "Failed to send to address." << std::endl;
        return;
    }

    if (socket.ready())
    {
        std::pair<std::optional<std::string>, std::pair<int, kt::SocketAddress>> recieved = socket.receiveFrom(testString.size());
        ASSERT_EQ(testString, recieved.first.value());
    }

    socket.close();
}

SIGPIPE Errors

SIGPIPE is a signal error raised by UNIX when you attempt to write data to a closed linux socket (closed by the remote). There are a few ways to work around this signal. Note: that in both cases, the kt::TCPSocket.send() function will return false in the result pair so you can detect that the send has failed. (You can refer to the TCPSocketTest.cpp file and the "...Linux..." related tests to do with "SIGPIPE" to find examples of the below).

1. Ignore SIGPIPE signals completely:

#include <csignal>

int main()
{
    std::signal(SIGPIPE, SIG_IGN);

    ...
}

2. Provide MSG_NOSIGNAL as the flag argument to the kt::TCPSocket.send() function which will ensure no signals are raised during the kt::TCPSocket.send() call.

#include <csignal>

...
kt::TCPSocket socket; // Initialise properly
...
if (!socket.send(std::string(message), MSG_NOSIGNAL).first)
{
    // Remote has closed connection, you can choose to close the current socket or any other work that is required when the connection is broken
}
...

3. Setup a handler function to be called with the SIGPIPE signal is raised.

#include <csignal>

void handleSignal(int signal)
{
    if (signal == SIGPIPE)
    {
        ...
    }
}

int main()
{
    // Set your handler function to be called when the signal is raised
    std::signal(SIGPIPE, handleSignal);
    ...

    // If you want to restore the default signal handling behaviour you can do the following
    std::signal(SIGPIPE, SIG_DFL);
}

NOTE: UDP Read Sizes

• Take care when reading UDP messages. If you do not read the entire length of the message the rest of the data will be lost.

Running the tests Dockerfile

The dockerfile is aimed at testing the socket behaviour across a few different flavours of linux to check it is functioning correctly. Especially since development is being done on WSL and there could be some slight differences.

docker build -f Environment-Test-Dockerfile .