QtcpSocket—QIODevice.write() sometimes return -1

hansflying

Dear all,

I set up a QtcpSocket to test my TCP based communication as follows:

QtcpSocket ipSocket = new QtcpScoket(this);
ipSocket->connectToHost(HostName, dataPort);
if(ipSocket->waitForConnected(5000ms))
{
	.........................
}
Else
{
	.......................
}

it works fine.

then I want to write some message to the TCP with following codes:

QIODevice m_ioDevice;
if((this->m_ioDevice != 0) && (this->m_ioDevice->isWritable())
{
	if(This.m_ioDevice->write(msg) == msg.count())
	{
		.........................
	}
	Else
	{
		........................
	}
}

it also works in most time. But sometimes the message can not be written to the IODevice, and the function This.m_ioDevice->write(msg) return -1.

I am not sure:

what does it mean when This.m_ioDevice->write(msg) returns -1 ?
why my code works fine in most time, only sometime the problem occurs?
how could I solve this problem?

thanks a lot for any of your suggestion and reply

best regards,
hansflying

koahnig

Welcome to devnet

I have added editor markdown tags for your code block. This makes it easier to read. Please have a look to the "Editor markdown tags" at the end of this page.

You can call error() and errorString(). From experience I guess that the connection broke down for whatever reason.

hansflying

thank you koahnig a lot!!

I will try your suggestion.

But the problem occurs sometimes. Whatever we will check it.