在WinInet编程中，SetOption函数用来设置超时，可经过测试，无效。在MSDN文档中明确指出“InternetSetOption Does Not Set Timeout Values”，微软提出的解决方法是用线程来实现，示例代码如下：
1 #include <windows.h>
2 #include <wininet.h>
3 #include <iostream.h>
4
5 DWORD WINAPI WorkerFunction( LPVOID );
6 HINTERNET g_hOpen, g_hConnect;
7
8 typedef struct
9 {
10 CHAR* pHost;
11 CHAR* pUser;
12 CHAR* pPass;
13 } PARM;
14
15 void main()
16 {
17 CHAR szHost[] = "localhost";
18 CHAR szUser[] = "JoeB";
19 CHAR szPass[] = "test";
20 CHAR szLocalFile[] = "localfile";
21 CHAR szRemoteFile[] = "remotefile";
22 DWORD dwExitCode;
23 DWORD dwTimeout;
24 PARM threadParm;
25
26 g_hOpen = 0;
27 if ( !( g_hOpen = InternetOpen ( "FTP sample",
28 LOCAL_INTERNET_ACCESS,
29 NULL,
30 0,
31 0 ) ) )
32 {
33 cerr << "Error on InternetOpen: " << GetLastError() << endl;
34 return ;
35 }
36
37 // Create a worker thread
38 HANDLE hThread;
39 DWORD dwThreadID;
40 threadParm.pHost = szHost;
41 threadParm.pUser = szUser;
42 threadParm.pPass = szPass;
43
44 hThread = CreateThread(
45 NULL, // Pointer to thread security attributes
46 0, // Initial thread stack size, in bytes
47 WorkerFunction, // Pointer to thread function
48 &threadParm, // The argument for the new thread
49 0, // Creation flags
50 &dwThreadID // Pointer to returned thread identifier
51 );
52
53 // Wait for the call to InternetConnect in worker function to complete
54 dwTimeout = 5000; // in milliseconds
55 if ( WaitForSingleObject ( hThread, dwTimeout ) == WAIT_TIMEOUT )
56 {
57 cout << "Can not connect to server in "
58 << dwTimeout << " milliseconds" << endl;
59 if ( g_hOpen )
60 InternetCloseHandle ( g_hOpen );
61 // Wait until the worker thread exits
62 WaitForSingleObject ( hThread, INFINITE );
63 cout << "Thread has exited" << endl;
64 return ;
65 }
66
67 // The state of the specified object (thread) is signaled
68 dwExitCode = 0;
69 if ( !GetExitCodeThread( hThread, &dwExitCode ) )
70 {
71 cerr << "Error on GetExitCodeThread: " << GetLastError() << endl;
72 return ;
73 }
74
75 CloseHandle (hThread);
76 if ( dwExitCode )
77 // Worker function failed
78 return ;
79
80 if ( !FtpGetFile ( g_hConnect,
81 szRemoteFile,
82 szLocalFile,
83 FALSE,INTERNET_FLAG_RELOAD,
84 FTP_TRANSFER_TYPE_ASCII,
85 0 ) )
86 {
87 cerr << "Error on FtpGetFile: " << GetLastError() << endl;
88 return ;
89 }
90
91 if ( g_hConnect )
92 InternetCloseHandle( g_hConnect );
93 if ( g_hOpen )
94 InternetCloseHandle( g_hOpen );
95
96 return ;
97 }
98
99 /////////////////// WorkerFunction //////////////////////
100 DWORD WINAPI
101 WorkerFunction(
102 IN LPVOID vThreadParm
103 )
104 /*
105 Purpose:
106 Call InternetConnect to establish a FTP session
107 Arguments:
108 vThreadParm - points to PARM passed to thread
109 Returns:
110 returns 0
111 */
112 {
113 PARM* pThreadParm;
114 // Initialize local pointer to void pointer passed to thread
115 pThreadParm = (PARM*)vThreadParm;
116 g_hConnect = 0;
117
118 if ( !( g_hConnect = InternetConnect (
119 g_hOpen,
120 pThreadParm->pHost,
121 INTERNET_INVALID_PORT_NUMBER,
122 pThreadParm->pUser,
123 pThreadParm->pPass,
124 INTERNET_SERVICE_FTP,
125 0,
126 0 ) ) )
127 {
128 cerr << "Error on InternetConnnect: " << GetLastError() << endl;
129 return 1; // failure
130 }
131
132 return 0; // success
133 }
134
一个老外写的同步类
W3C w3csample