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POTCP socket communications are being corrupted
 

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  1. POTCP socket communications are being corrupted
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    <p>I am trying to use a TCP server and connect to it with a QTcpSocket client. Most of the time, the server and client happen to be on the same machine, but this is not a requirement. What I am trying to do is transfer a file from a running multithreaded process to a GUI that wants to share information used by both the server and the client.</p> <p>The connect, etc seems to be just fine. In fact, the code appeared to work perfectly for a long time, but now that I am running it on different hardware, and on Ubuntu 12.04 instead of 10.04, I am occasionally getting embedded stray bytes in the received code--usually (but not always) nulls. I cant figure out whats wrong, and would welcome any advice.</p> <p>Here is portion of the server that reads my file and sends the bytes to the connected client:</p> <pre><code>int fileSize; printf(" about to open the file\n"); ini_fd = fopen (rov_ini_file_name, "r"); if(!ini_fd){ break; } fseek(ini_fd,0,SEEK_END); fileSize = ftell(ini_fd); fseek(ini_fd,0,SEEK_SET); int totalBytesSent =0; int line = 0; int len; while (!feof (ini_fd)) { ch = fgets (&amp;(my_line[0]), MAX_CHARACTER_COUNT - 1, ini_fd); if (ch){ len = strlen(&amp;(my_line[0])); bytes_sent = sendto(tio.my_tio_port_table_entry.to_sock, &amp;(my_line[0]), len, 0, (struct sockaddr *) (&amp;(tio.my_tio_port_table_entry.ToAddr)), sizeof (tio.my_tio_port_table_entry.ToAddr)); totalBytesSent += bytes_sent; line++; //printf(" line %d bytes sent = %d total bytes = %d\n",line,bytes_sent,totalBytesSent); } } len = sprintf(&amp;(my_line[0]),"END_OF_INI_FILE"); bytes_sent = sendto(tio.my_tio_port_table_entry.to_sock, &amp;(my_line[0]), len, 0, (struct sockaddr *) (&amp;(tio.my_tio_port_table_entry.ToAddr)), sizeof (tio.my_tio_port_table_entry.ToAddr)); tio.my_tio_port_table_entry.connected = FALSE; break; </code></pre> <p>Here is where I read the data being sent. This is the slot connected to the readyRead signal</p> <pre><code> void AlvGUI::readIniFromServer() { QByteArray inArray(iniClient-&gt;bytesAvailable(),0); if(!iniStarted) { tempIniFile = new QTemporaryFile; if(tempIniFile-&gt;open()) { iniStarted = true; } else { // error should be here! } } int bytesRead = iniClient-&gt;read(inArray.data(),inArray.size()); int endLoc = inArray.lastIndexOf("END_OF_INI_FILE"); if(-1 != endLoc) { inArray.chop(endLoc); bytesRead = endLoc; iniFinished = true; } tempIniFile-&gt;write(inArray.data(),bytesRead); if(iniFinished) { tempIniFile-&gt;flush(); tempIniFile-&gt;close(); iniFile.close_ini(); char *theTempFile = strdup((char *)tempIniFile-&gt;fileName().toAscii().data()); iniFile.open_ini(theTempFile); gotIni = true; iniRequestTimer-&gt;stop(); makeGui(); free(theTempFile); hotelSetup = true; iniClient-&gt;abort(); } } </code></pre>
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    1. COI should add that the file being sent is an ascii text file. As might be expected with TCP, I am sending it line by line and it is being received in a different chunkiness.
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      1. USjhowland
    2. CO`iniClient->bytesAvailable()`. Get rid of this. Use a fixed size data buffer. There are very few correct use of this method and this isn't one of them.
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    3. COcan you explain why bytesAvailable() is bad to use here? I started doing this as a result of copying TrollTech example code, and haven't found problems--I realize that doesn't mean there aren't problems, but if this is a well known problematic approach, I'd like to see discussion. I have done a google search with no immediate explanations
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