Native Messaging host not able to send 1 MB data

Question

I am using the native-host in C++, when i send base64 from the native app to chrome extension(Native messaging) with size base64 < 1M, the program is still running. but when i send base64 from the native app to chrome extension (Native messaging) with size base64 >1M, the program is error "Error when communicating with the native messaging host" my code below

int _tmain(int argc, _TCHAR* argv[])
{
    std::cout.setf( std::ios_base::unitbuf );
    unsigned int c, t=0;
    inp="";
    t=0;
    // Sum the first 4 chars from stdin (the length of the message passed).
    for (int i = 0; i <= 3; i++) {
        //t += getchar();
        t += std::pow(256.0f, i) * getchar();
    }
    // Loop getchar to pull in the message until we reach the total
    //  length provided.
    for (int i=0; i < t; i++) {
        c = getchar();
        inp += c;
    }

    unsigned int len =  inp.length();
    // We need to send the 4 btyes of length information
    std::cout << char(((len>>0) & 0xFF))
              << char(((len>>8) & 0xFF))
              << char(((len>>16) & 0xFF))
              << char(((len>>24) & 0xFF));
    // Now we can output our message
    std::cout << inp;
    return 0;
}

Yeah, this is by design, they simply don't accept messages greater than 1M. You need to break it down into a series of smaller messages and re-assemble the data in the extension. — donaddon

Rob W Rob W · Accepted Answer · 2014-12-02T23:01:35

Native messaging hosts cannot send a message with more than 1024*1024 bytes. From

https://cs.chromium.org/file%3Anative_message_process_host.cc%20kMaximumMessageSize:

// Maximum message size in bytes for messages received from Native Messaging
// hosts. Message size is limited mainly to prevent Chrome from crashing when
// native application misbehaves (e.g. starts writing garbage to the pipe).
const size_t kMaximumMessageSize = 1024 * 1024;

To work around this problem, you have to split the message sent from the native messaging host to your extension/app in chunks of less than 1MB.
In your native messaging host, you could create a loop that repeatedly outputs the 32-bit message length (max 1MB) followed by a chunk of the message.
In your app/extension, use chrome.runtime.connectNative instead of chrome.runtime.sendNativeMessage to open a port that lasts longer than one message (if you use sendNativeMessage, the port will be closed after receiving one reply, which causes the native messaging host to terminate).

Native Messaging host not able to send 1 MB data

1 Answers