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<html><head><meta http-equiv="Content-Language" content="en-us"><meta http-equiv="Content-Type" content="text/html; charset=windows-1252"><title>UDT Reference</title></head><body><table border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse" width="100%" id="table1" bgcolor="#99CCFF" bordercolor="#99CCFF"> <tr> <td width="100%"><font face="Verdana" size="2"><i> UDT </i></font><i> <font face="Verdana" size="2">Tutorial</font></i></td> </tr></table><h1><font face="Verdana" size="4">Error Handling</font></h1><p><font face="Verdana" size="2">All UDT API will return an error upon a failed operation. Particularly, UDT defines <b>UDT::INVALID_SOCK</b> and <b>UDT::ERROR</b> as error returned values. Application should check the return value against these two constants (several routine return <b>false</b> as error value).</font></p><p><font face="Verdana" size="2">On error, <a href="error.htm">getlasterror</a> can be used to retrieve the error information. In fact, the function returns the latest error occurred in the thread where the function is called. <a href="error.htm">getlasterror</a> returns a<a href="structure.htm#UDTERROR">ERRORINFO</a> structure, it contains both the error code and special text error message. Two helper functions of <u><b>getErrorCode</b></u> and <u><b>getErrorMessage</b></u> can be used to read these information.</font></p><h4><font face="Verdana" size="2">Examples</font></h4><table border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse" width="100%" id="table2" bgcolor="#C0C0C0" bordercolor="#C0C0C0"> <tr> <td width="100%"> <p style="margin-top: 0; margin-bottom: 0"> <font face="Courier New" size="1">sockaddr_in my_addr;<br> my_addr.sin_family = AF_INET;<br> my_addr.sin_port = htons(21); //invalid port number<br> my_addr.sin_addr.s_addr = INADDR_ANY;<br> memset(&(my_addr.sin_zero), '\0', 8);<br> </font><p style="margin-top: 0; margin-bottom: 0"> <font face="Courier New" size="1">UDTSOCKET serv = UDT::socket(AF_INET, SOCK_STREAM, 0);<br> if (UDT::ERROR == UDT::bind(serv, (sockaddr*)&my_addr, sizeof(my_addr)))<br> {<br> cout << "bind: " << UDT::getlasterror().getErrorMessage();</font><p style="margin-top: 0; margin-bottom: 0"> <p style="margin-top: 0; margin-bottom: 0"> <font face="Courier New" size="1"> // further action may depends on UDT::getlasterror().getErrorCode().</font><p style="margin-top: 0; margin-bottom: 0"> <font face="Courier New" size="1"> // system level error can be accessed through "errno"</font><p style="margin-top: 0; margin-bottom: 0"> <font face="Courier New" size="1"><br> return 0;<br> }</font></td> </tr></table><p><font face="Verdana" size="2">In the example above, the output will be:</font></p><table border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse" width="100%" id="table3" bgcolor="#C0C0C0" bordercolor="#C0C0C0"> <tr> <td width="100%"> <font face="Verdana" size="1">error message: Couldn't set up network connection: Permission denied.</font></td> </tr></table><p><font face="Verdana" size="2">The UDT error code only reflects the operation error of the UDT socket level. Applications can still read the system level error (e.g.,<u>errno</u> in Linux, <u>GetLastError</u> in Windows) to read more specific error information. However, the error message obtained by <u>getErrorMessage</u> contains information of both the UDT level error and the system level error.</font></p></body></html>⌨️ 快捷键说明
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