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copied!<p>You are calling <code>WSAStartup()</code> twice, which will require you to call <code>WSACleanup()</code> twice to unload WinSock correctly. You should only be calling <code>WSAStartup()</code> once.</p> <p>The <code>szProtocol</code> member of the <code>WSAPROTOCOL_INFO</code> structure is an array of <code>TCHAR</code> elements. <code>TCHAR</code> maps to <code>char</code> or <code>wchar_t</code> depending on whether the calling app is compiled for ANSI/MBCS or UNICODE. That is why there is no <code>WSAEnumProtocols()</code> function in ws2_32.dll. There are separate <code>WSAEnumProtocolsA()</code> (for Ansi) and <code>WSAEnumProtocolsW()</code> (for Unicode) functions instead. Since Java uses Unicode strings, you should have your JNA code use <code>WSAEnumProtocolsW()</code>. <code>WSAStartup()</code> does not use <code>TCHAR</code>, only <code>char</code>, which is why there are no separate <code>WSAStartupA()</code> and <code>WSAStartupW()</code> functions for it.</p> <p>If your JNA code is not able to get <code>WSAEnumProtocols()</code> and <code>WSAGetLastError()</code> working correctly, its likely that you are are declaring/using them wrong, but you did not show any of that code, so nobody can say for sure why it is not working for you.</p> <p><strong>Update:</strong> try something like this (I don't use JNA, so this may need some tweaking, but this will give you the general idea):</p> <pre><code>public interface Ws2_32 extends Library { // I don't know how to declare fixed size arrays in JNA, // so you will have to adjust these Structue declarations // as needed... public static class WSAData extends Structure { short wVersion; short wHighVersion; byte szDescription[257]; byte szSystemStatus[129]; short iMaxSockets; short iMaxUdpDg; String lpVendorInfo; }; public static class WSAPROTOCOLCHAIN extends Structure { int ChainLen; int ChainEntries[7]; }; public static class WSAPROTOCOL_INFOW extends Structure { int dwServiceFlags1; int dwServiceFlags2; int dwServiceFlags3; int dwServiceFlags4; int dwProviderFlags; GUID ProviderId; int dwCatalogEntryId; WSAPROTOCOLCHAIN ProtocolChain; int iVersion; int iAddressFamily; int iMaxSockAddr; int iMinSockAddr; int iSocketType; int iProtocol; int iProtocolMaxOffset; int iNetworkByteOrder; int iSecurityScheme; int dwMessageSize; int dwProviderReserved; char szProtocol[256]; }; Ws2_32 INSTANCE = (Ws2_32) Native.loadLibrary("ws2_32", Ws2_32.class); int WSAStartup(short version, WSADATA lpwsaData); int WSAEnumProtocolsW(int[] lpiProtocols, WSAPROTOCOL_INFOW[] lpProtocolBuffer, IntByReference lpdwBufferLength); int WSACleanup(); int WSAGetLastError(); int WSASetLastError(int iError); } </code></pre> <p>.</p> <pre><code>public static void main(String[] args){ WSADATA wsaData = new WSADATA(); short version = 2; int result = Ws2_32.INSTANCE.WSAStartup(version, wsaData); System.out.println("WSAStartup() returned: " + result); if(result == 0){ System.out.println("WSADATA struct:"); System.out.println("wVersion: " + wsaData.wVersion); System.out.println("wHighVersion: " + wsaData.wHighVersion); System.out.print("szDescription: "); for(byte b : wsaData.szDescription){ System.out.print((char) b); } System.out.print("\n"); System.out.print("szSystemStatus: "); for(byte b : wsaData.szSystemStatus){ System.out.print((char) b); } System.out.print("\n"); System.out.println("iMaxSockets: " + wsaData.iMaxSockets); System.out.println("iMaxUdpDg: " + wsaData.iMaxUdpDg"); } } </code></pre> <p>.</p> <pre><code>public class TestWSAEnumProtocolsA { public void start(){ WSAPROTOCOL_INFOW[] wsaprotocol_info = new WSAPROTOCOL_INFOW[1]; WSADATA wsaData = new WSADATA(); IntByReference dwBufferLength = new IntByReference(628); // sizeof WSAPROTOCOL_INFOW, in bytes int result = 0; short version = 2; if((result = Ws2_32.INSTANCE.WSAStartup(version, wsaData)) != 0){ System.out.println("Error #" + result + " at WSAStartup()"); return; } System.out.println("WSAStartup() finished correctly."); if((result = Ws2_32.INSTANCE.WSAEnumProtocolsW(null, wsaprotocol_info, dwBufferLength)) == -1){ System.out.println("WSAEnumProtocolsW() returned: " + result); System.out.println("dwBufferLength is: " + dwBufferLength.getValue()); System.out.println("WSAGetLastError() returned: " + Ws2_32.INSTANCE.WSAGetLastError()); } } } </code></pre>

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