在有线的连接和WIFI都不可用的时候, .NET CF的HttpWebRequest会由于web requests/web services 而自动设置GPRS连接。所以实际上当你发起一个Web请求或者连接Webservice的时候，并不需要开发者编码处理GPRS的连接问题。不过对于更低层的通信，如使用TcpClient 和 UdpClient的时候，则需要为咩使用 Connection Manager API来建立和释放连接。 (本文英文原文见：http://blogs.msdn.com/anthonywong/archive/2006/03/13/550686.aspx)
以下托管类是对Connection Manager API的封装
public class GPRSConnection
{
const int S_OK = 0;
const uint CONNMGR_PARAM_GUIDDESTNET = 0x1;
const uint CONNMGR_FLAG_PROXY_HTTP = 0x1;
const uint CONNMGR_PRIORITY_USERINTERACTIVE = 0x08000;
const uint INFINITE = 0xffffffff;
const uint CONNMGR_STATUS_CONNECTED = 0x10;
static Hashtable ht = new Hashtable();
static GPRSConnection()
{
ManualResetEvent mre = new ManualResetEvent(false);
mre.Handle = ConnMgrApiReadyEvent();
mre.WaitOne();
CloseHandle(mre.Handle);
}
~GPRSConnection()
{
ReleaseAll();
}
public static bool Setup(Uri url)
{
return Setup(url.ToString());
}
public static bool Setup(string urlStr)
{
ConnectionInfo ci = new ConnectionInfo();
IntPtr phConnection = IntPtr.Zero;
uint status = 0;
if (ht[urlStr] != null)
return true;
if (ConnMgrMapURL(urlStr, ref ci.guidDestNet, IntPtr.Zero) != S_OK)
return false;
ci.cbSize = (uint) Marshal.SizeOf(ci);
ci.dwParams = CONNMGR_PARAM_GUIDDESTNET;
ci.dwFlags = CONNMGR_FLAG_PROXY_HTTP;
ci.dwPriority = CONNMGR_PRIORITY_USERINTERACTIVE;
ci.bExclusive = 0;
ci.bDisabled = 0;
ci.hWnd = IntPtr.Zero;
ci.uMsg = 0;
ci.lParam = 0;
if (ConnMgrEstablishConnectionSync(ref ci, ref phConnection, INFINITE, ref status) != S_OK &&
status != CONNMGR_STATUS_CONNECTED)
return false;
ht[urlStr] = phConnection;
return true;
}
public static bool Release(Uri url)
{
return Release(url.ToString());
}
public static bool Release(string urlStr)
{
return Release(urlStr, true);
}
private static bool Release(string urlStr, bool removeNode)
{
bool res = true;
IntPtr ph = IntPtr.Zero;
if (ht[urlStr] == null)
return true;
ph = (IntPtr)ht[urlStr];
if (ConnMgrReleaseConnection(ph, 1) != S_OK)
res = false;
CloseHandle(ph);
if (removeNode)
ht.Remove(urlStr);
return res;
}
public static void ReleaseAll()
{
foreach(DictionaryEntry de in ht)
{
Release((string)de.Key, false);
}
ht.Clear();
}
[StructLayout(LayoutKind.Sequential)]
public struct ConnectionInfo
{
public uint cbSize;
public uint dwParams;
public uint dwFlags;
public uint dwPriority;
public int bExclusive;
public int bDisabled;
public Guid guidDestNet;
public IntPtr hWnd;
public uint uMsg;
public uint lParam;
public uint ulMaxCost;
public uint ulMinRcvBw;
public uint ulMaxConnLatency;
}
[DllImport("cellcore.dll")]
private static extern int ConnMgrMapURL(string pwszURL, ref Guid pguid, IntPtr pdwIndex);
[DllImport("cellcore.dll")]
private static extern int ConnMgrEstablishConnectionSync(ref ConnectionInfo ci, ref IntPtr phConnection, uint dwTimeout, ref uint pdwStatus);
[DllImport("cellcore.dll")]
private static extern IntPtr ConnMgrApiReadyEvent();
[DllImport("cellcore.dll")]
private static extern int ConnMgrReleaseConnection(IntPtr hConnection, int bCache);
[DllImport("coredll.dll")]
private static extern int CloseHandle(IntPtr hObject);
}
使用GPRSConnection class的时候, 先调用Setup方法创建连接，见以下代码:
public void DoTcpConnection()
{
string url = "www.msn.com";
bool res = GPRSConnection.Setup("http://" + url + "/");
if (res)
{
TcpClient tc = new TcpClient(url, 80);
NetworkStream ns = tc.GetStream();
byte[] buf = new byte[100];
ns.Write(buf, 0, 100);
tc.Client.Shutdown(SocketShutdown.Both);
ns.Close();
tc.Close();
MessageBox.Show("Wrote 100 bytes");
}
else
{
MessageBox.Show("Connection establishment failed");
}
}