表A.1列出了WSAGetLastError()函數(shù)返回的可能錯誤碼和它們的解釋，它們可分為四個部分。

     錯誤碼的第一部分是用來解決在不同的C編譯中對標(biāo)準(zhǔn)C錯誤碼的不一致的定義。錯誤碼的第二部分是標(biāo)準(zhǔn)Berkeley Sockets錯誤碼的Windows Sockets版本。錯誤碼的第三部分包括特定Windows Sockets擴(kuò)充的錯誤碼。錯誤碼的第四部分由Windows Sockets的getXbyY()和WSAAsyncGetXByY()函數(shù)返回，相當(dāng)于Berkeley軟件中由變量h_errno返回的錯誤（事實(shí)上，Windows Sockets在頭文件winsock.h中已將h_error定義成其值為WSAGetLastError()的一個宏），它們相當(dāng)于由域名服務(wù)（Domain Name Service）返回的各種失敗。如果Windows Sockets實(shí)現(xiàn)沒有使用域名服務(wù)，它將使用最合適的代碼。一般地，Windows Sockets應(yīng)用程序應(yīng)該將錯誤WSAHOST_NOT_FOUND和WSANO_DATA解釋為指示關(guān)鍵字（名字，地址等）沒有找著，而錯誤WSATRY_AGAIN和WSANO_RECOVERY是提醒名字服務(wù)自身是非操作的。

     錯誤碼由Windows Sockets 規(guī)范定義，在所有同一版本規(guī)范的Windows Sockets兼容實(shí)現(xiàn)中，它們是一致的。

 

表A.1  Windows Sockets錯誤碼

 

     下面給出WSAGetLastError()函數(shù)返回的可能錯誤碼按字母順序排列的列表，同時給出簡要的擴(kuò)展描述。

WSAEACCES                          (10013)             Permission denied.

試圖使用被禁止的訪問權(quán)限去訪問套接字。例如，在沒有使用函數(shù)setsockopt()的SO_BROADCAST命令設(shè)置廣播權(quán)限的套接字上使用函數(shù)sendto()給一個廣播地址發(fā)送數(shù)據(jù)。

 

WSAEADDRINUSE                 (10048)             Address already in use.

正常情況下每一個套接字地址（協(xié)議／IP地址／端口號）只允許使用一次。當(dāng)應(yīng)用程序試圖使用bind()函數(shù)將一個被已存在的或沒有完全關(guān)閉的或正在關(guān)閉的套接字使用了的IP地址／端口號綁扎到一個新套接字上時，該錯誤發(fā)生。對于服務(wù)器應(yīng)用程序來說，如果需要使用bind()函數(shù)將多個套接字綁扎到同一個端口上，可以考慮使用setsockopt()函數(shù)的SO_REUSEADDR命令。客戶應(yīng)用程序一般不必使用bind()函數(shù)——connect()函數(shù)總是自動選擇沒有使用的端口號。當(dāng)bind()函數(shù)操作的是通配地址（包括ADDR_ANY）時，錯誤WSAEADDRINUSE可能延遲到一個明確的地址被提交時才發(fā)生。這可能在后續(xù)的函數(shù)如connect()、listen()、WSAConnect()或WSAJoinLeaf()調(diào)用時發(fā)生。

 

WSAEADDRNOTAVAIL         (10049)             Cannot assign requested address.

被請求的地址在它的環(huán)境中是不合法的。通常地在bind()函數(shù)試圖將一個本地機(jī)器不合法的地址綁扎到套接字時產(chǎn)生。它也可能在connect()、sendto()、WSAConnect()、WSAJoinLeaf()或WSASendTo()函數(shù)調(diào)用時因遠(yuǎn)程機(jī)器的遠(yuǎn)程地址或端口號非法（如0地址或0端口號）而產(chǎn)生。

 

WSAEAFNOSUPPORT            (10047)             Address family not supported by protocol family.

使用的地址與被請求的協(xié)議不兼容。所有的套接字在創(chuàng)建時都與一個地址族（如IP協(xié)議對應(yīng)的AF_INET）和一個通用的協(xié)議類型（如SOCK_STREAM）聯(lián)系起來。如果在socket()調(diào)用中明確地要求一個不正確的協(xié)議，或在調(diào)用sendto()等函數(shù)時使用了對套接字來說是錯誤的地址族的地址，該錯誤返回。

 

WSAEALREADY                    (10037)             Operation already in progress.

當(dāng)在非阻塞套接字上已經(jīng)有一個操作正在進(jìn)行時，又有一個操作試圖在其上執(zhí)行則產(chǎn)生此錯誤。如：在一個正在進(jìn)行連接的非阻塞套接字上第二次調(diào)用connect()函數(shù)；或取消一個已經(jīng)被取消或已完成的異步請求（WSAAsyncGetXbyY()）。

 

WSAECONNABORTED           (10053)             Software caused connection abort.

一個已建立的連接被你的主機(jī)上的軟件終止，可能是因?yàn)橐淮螖?shù)據(jù)傳輸超時或是協(xié)議錯誤。

 

WSAECONNREFUSED            (10061)             Connection refused.

因?yàn)槟繕?biāo)主機(jī)主動拒絕，連接不能建立。這通常是因?yàn)樵噲D連接到一個遠(yuǎn)程主機(jī)上不活動的服務(wù)，如沒有服務(wù)器應(yīng)用程序處于執(zhí)行狀態(tài)。

 

WSAECONNRESET                (10054)             Connection reset by peer.

存在的連接被遠(yuǎn)程主機(jī)強(qiáng)制關(guān)閉。通常原因?yàn)椋哼h(yuǎn)程主機(jī)上對等方應(yīng)用程序突然停止運(yùn)行，或遠(yuǎn)程主機(jī)重新啟動，或遠(yuǎn)程主機(jī)在遠(yuǎn)程方套接字上使用了“強(qiáng)制”關(guān)閉（參見setsockopt(SO_LINGER)）。另外，在一個或多個操作正在進(jìn)行時，如果連接因“keep-alive”活動檢測到一個失敗而中斷，也可能導(dǎo)致此錯誤。此時，正在進(jìn)行的操作以錯誤碼WSAENETRESET失敗返回，后續(xù)操作將失敗返回錯誤碼WSAECONNRESET。

 

WSAEDESTADDRREQ           (10039)             Destination address required.

在套接字上一個操作所必須的地址被遺漏。例如，如果sendto()函數(shù)被調(diào)用且遠(yuǎn)程地址為ADDR_ANY時，此錯誤被返回。

 

WSAEFAULT                          (10014)             Bad address.

系統(tǒng)檢測到調(diào)用試圖使用的一個指針參數(shù)指向的是一個非法指針地址。如果應(yīng)用程序傳遞一個非法的指針值，或緩沖區(qū)長度太小，此錯誤發(fā)生。例如，參數(shù)為結(jié)構(gòu)sockaddr，但參數(shù)的長度小于sizeof(struct sockaddr)。

 

WSAEHOSTDOWN                 (10064)             Host is down.

套接字操作因?yàn)槟康闹鳈C(jī)關(guān)閉而失敗返回。套接字操作遇到不活動主機(jī)。本地主機(jī)上的網(wǎng)絡(luò)活動沒有初始化。這些條件由錯誤碼WSAETIMEDOUT指示似乎更合適。

 

WSAEHOSTUNREACH           (10065)             No route to host.

試圖和一個不可達(dá)主機(jī)進(jìn)行套接字操作。參見WSAENETUNREACH。

 

WSAEINPROGRESS               (10036)             Operation now in progress.

一個阻塞操作正在執(zhí)行。Windows Sockets只允許一個任務(wù)（或線程）在同一時間可以有一個未完成的阻塞操作，如果此時調(diào)用了任何函數(shù)（不管此函數(shù)是否引用了該套接字或任何其它套接字），此函數(shù)將以錯誤碼WSAEINPROGRESS返回。

 

WSAEINTR                            (10004)             Interrupted function call.

阻塞操作被函數(shù)WSACancelBlockingCall ()調(diào)用所中斷。

 

WSAEINVAL                           (10022)             Invalid argument.

提供了非法參數(shù)（例如，在使用setsockopt()函數(shù)時指定了非法的level）。在一些實(shí)例中，它也可能與套接字的當(dāng)前狀態(tài)相關(guān)，例如，在套接字沒有使用listen()使其處于監(jiān)聽時調(diào)用accept()函數(shù)。

 

WSAEISCONN                        (10056)             Socket is already connected.

連接請求發(fā)生在已經(jīng)連接的套接字上。一些實(shí)現(xiàn)對于在已連接SOCK_DGRAM套接字上使用sendto()函數(shù)的情況也返回此錯誤（對于SOCK_STREAM套接字，sendto()函數(shù)的to參數(shù)被忽略），盡管其它一些實(shí)現(xiàn)將此操作視為合法事件。

 

WSAEMFILE                          (10024)             Too many open files.

打開了太多的套接字。不管是對整個系統(tǒng)還是每一進(jìn)程或線程，Windows Sockets實(shí)現(xiàn)都可能有一個最大可用的套接字句柄數(shù)。

 

WSAEMSGSIZE                      (10040)             Message too long.

在數(shù)據(jù)報套接字上發(fā)送的一個消息大于內(nèi)部消息緩沖區(qū)或一些其它網(wǎng)絡(luò)限制，或者是用來接受數(shù)據(jù)報的緩沖區(qū)小于數(shù)據(jù)報本身。

 

WSAENETDOWN                    (10050)             Network is down.

套接字操作遇到一個不活動的網(wǎng)絡(luò)。此錯誤可能指示網(wǎng)絡(luò)系統(tǒng)（例如WinSock DLL運(yùn)行的協(xié)議棧）、網(wǎng)絡(luò)接口或本地網(wǎng)絡(luò)本身發(fā)生了一個嚴(yán)重的失敗。

 

WSAENETRESET                   (10052)             Network dropped connection on reset.

在操作正在進(jìn)行時連接因“keep-alive”檢測到失敗而中斷。也可能由setsockopt()函數(shù)返回，如果試圖使用它在一個已經(jīng)失敗的連接上設(shè)置SO_KEEPALIVE。

 

WSAENETUNREACH              (10051)             Network is unreachable.

試圖和一個無法到達(dá)的網(wǎng)絡(luò)進(jìn)行套接字操作。它常常意味著本地軟件不知道到達(dá)遠(yuǎn)程主機(jī)的路由。

 

WSAENOBUFS                        (10055)             No buffer space available.

由于系統(tǒng)缺乏足夠的緩沖區(qū)空間，或因?yàn)殛?duì)列已滿，在套接字上的操作無法執(zhí)行。

 

WSAENOPROTOOPT             (10042)             Bad protocol option.

在getsockopt()或setsockopt()調(diào)用中，指定了一個未知的、非法的或不支持的選項(xiàng)或?qū)樱╨evel）。

 

WSAENOTCONN                    (10057)             Socket is not connected.

因?yàn)樘捉幼譀]有連接，發(fā)送或接收數(shù)據(jù)的請求不被允許，或者是使用sendto()函數(shù)在數(shù)據(jù)報套接字上發(fā)送時沒有提供地址。任何其它類型的操作也可以返回此錯誤，例如，使用setsockopt()函數(shù)在一個已重置的連接上設(shè)置SO_KEEPALIVE。

 

WSAENOTSOCK                    (10038)             Socket operation on non-socket.

操作試圖不是在套接字上進(jìn)行。它可能是套接字句柄參數(shù)沒有引用到一個合法套接字，或者是調(diào)用select()函數(shù)時，一個fd_set中的成員不合法。

 

WSAEOPNOTSUPP                (10045)             Operation not supported.

對于引用的對象的類型來說，試圖進(jìn)行的操作不支持。通常它發(fā)生在套接字不支持此操作的套接字描述符上，例如，試圖在數(shù)據(jù)報套接字上接收連接。

 

WSAEPFNOSUPPORT            (10046)             Protocol family not supported.

協(xié)議簇沒有在系統(tǒng)中配置或沒有支持它的實(shí)現(xiàn)存在。它與WSAEAFNOSUPPORT有些微的不同，但在絕大多數(shù)情況下是可互換的，返回這兩個錯誤的所有Windows Sockets函數(shù)的說明見WSAEAFNOSUPPORT的描述。

 

WSAEPROCLIM                     (10067)             Too many processes.

Windows Sockets實(shí)現(xiàn)可能限制同時使用它的應(yīng)用程序的數(shù)量，如果達(dá)到此限制，WSAStartup()函數(shù)可能因此錯誤失敗。

 

WSAEPROTONOSUPPORT     (10043)             Protocol not supported.

請求的協(xié)議沒有在系統(tǒng)中配置或沒有支持它的實(shí)現(xiàn)存在。例如，socket()調(diào)用請求一個SOCK_DGRAM套接字，但指定的是流協(xié)議。

 

WSAEPROTOTYPE                (10041)             Protocol wrong type for socket.

在socket()函數(shù)調(diào)用中指定的協(xié)議不支持請求的套接字類型的語義。例如，ARPA Internet UDP協(xié)議不能和SOCK_STREAM套接字類型一同指定。

 

WSAESHUTDOWN                 (10058)             Cannot send after socket shutdown.

因?yàn)樘捉幼衷谙鄳?yīng)方向上已經(jīng)被先前的shutdown()調(diào)用關(guān)閉，因此該方向上的發(fā)送或接收請求不被允許。通過調(diào)用shutdown()函數(shù)來請求對套接字的部分關(guān)閉，它發(fā)送一個信號來停止發(fā)送或接收或雙向操作。

 

WSAESOCKTNOSUPPORT    (10044)             Socket type not supported.

不支持在此地址族中指定的套接字類型。例如，socket()調(diào)用中選擇了可選的套接字類型SOCK_RAW，但是實(shí)現(xiàn)卻根本不支持SOCK_RAW類型的套接字。

 

WSAETIMEDOUT                   (10060)             Connection timed out.

連接請求因被連接方在一個時間周期內(nèi)不能正確響應(yīng)而失敗，或已經(jīng)建立的連接因被連接的主機(jī)不能響應(yīng)而失敗。

 

WSATYPE_NOT_FOUND        (10109)             Class type not found

     指定的類沒有找到。

 

WSAEWOULDBLOCK           (10035)             Resource temporarily unavailable.

此錯誤由在非阻塞套接字上不能立即完成的操作返回，例如，當(dāng)套接字上沒有排隊(duì)數(shù)據(jù)可讀時調(diào)用了recv()函數(shù)。此錯誤不是嚴(yán)重錯誤，相應(yīng)操作應(yīng)該稍后重試。對于在非阻塞SOCK_STREAM套接字上調(diào)用connect()函數(shù)來說，報告WSAEWOULDBLOCK是正常的，因?yàn)榻⒁粋€連接必須花費(fèi)一些時間。

 

WSAHOST_NOT_FOUND        (11001)             Host not found.

主機(jī)未知。此名字不是一個正式主機(jī)名，也不是一個別名，它不能在查詢的數(shù)據(jù)庫中找到。此錯誤也可能在協(xié)議和服務(wù)查詢中返回，它意味著指定的名字不能在相關(guān)數(shù)據(jù)庫中找到。

 

WSA_INVALID_HANDLE        (OS dependent) Specified event object handle is invalid.

應(yīng)用程序試圖使用一個事件對象，但指定的句柄非法。

 

WSA_INVALID_PARAMETER (OS dependent) One or more parameters are invalid.

應(yīng)用程序使用了一個直接映射到Win32函數(shù)的WinSock函數(shù)，而Win32函數(shù)指示一個或多個參數(shù)有問題。

 

WSAINVALIDPROCTABLE    (OS dependent)      Invalid procedure table from service provider.

服務(wù)提供者返回了一個假的WS2_32.DLL程序（procedure）表。這通常是由一個或多個函數(shù)指針為空引起。

 

WSAINVALIDPROVIDER        (OS dependent)      Invalid service provider version number.

     服務(wù)提供者返回一個不同于2.2的版本號。

 

WSA_IO_INCOMPLETE         (OS dependent) Overlapped I/O event object not in signaled state.

應(yīng)用程序試圖檢測一個沒有完成的重疊操作的狀態(tài)。應(yīng)用程序使用函數(shù)WSAGetOverlappedResult()（參數(shù)fWait設(shè)置為false）以輪詢模式檢測一個重疊操作是否完成時將得到此錯誤碼，除非該操作已經(jīng)完成。

 

WSA_IO_PENDING                 (OS dependent) Overlapped operations will complete later.

應(yīng)用程序已經(jīng)初始化了一個不能立即完成的重疊操作。當(dāng)稍后此操作完成時將有完成指示。

 

WSA_NOT_ENOUGH_MEMORY  (OS dependent)       Insufficient memory available.

應(yīng)用程序使用了一個直接映射到Win32函數(shù)的WinSock函數(shù)，而Win32函數(shù)指示缺乏必要的內(nèi)存資源。

 

WSANOTINITIALISED           (10093)             Successful WSAStartup() not yet performed.

應(yīng)用程序沒有調(diào)用WSAStartup()函數(shù)，或函數(shù)WSAStartup()調(diào)用失敗了。應(yīng)用程序可能訪問了不屬于當(dāng)前活動任務(wù)的套接字（例如試圖在任務(wù)間共享套接字），或調(diào)用了過多的WSACleanup()函數(shù)。

 

WSANO_DATA                        (11004)             Valid name, no data record of requested type.

請求的名字合法并且在數(shù)據(jù)庫中找到了，但它沒有正確的關(guān)聯(lián)數(shù)據(jù)用于解析。此錯誤的通常例子是主機(jī)名到地址（使用gethostbyname()或WSAAsyncGetHostByName()函數(shù)）的DNS轉(zhuǎn)換請求，返回了MX（Mail eXchanger）記錄但是沒有A（Address）記錄，它指示主機(jī)本身是存在的，但是不能直接到達(dá)。

 

WSANO_RECOVERY              (11003)             This is a non-recoverable error.

此錯誤碼指示在數(shù)據(jù)庫查找時發(fā)生了某種不可恢復(fù)錯誤。它可能是因?yàn)閿?shù)據(jù)庫文件（如BSD兼容的HOSTS、SERVICES或PROTOCOLS文件）找不到，或DNS請求應(yīng)服務(wù)器有嚴(yán)重錯誤而返回。

 

WSAPROVIDERFAILEDINIT  (OS dependent)      Unable to initialize a service provider.

服務(wù)提供者的DLL不能加載（LoadLibrary()失敗）或提供者的WSPStartup/NSPStartup函數(shù)失敗。

 

WSASYSCALLFAILURE         (OS dependent)      System call failure..

當(dāng)一個不應(yīng)該失敗的系統(tǒng)調(diào)用失敗時返回。例如，如果WaitForMultipleObjects()調(diào)用失敗，或注冊的API不能夠利用協(xié)議／名字空間目錄。

 

WSASYSNOTREADY              (10091)             Network subsystem is unavailable.

此錯誤由WSAStartup()函數(shù)返回，它表示此時Windows Sockets實(shí)現(xiàn)因底層用來提供網(wǎng)絡(luò)服務(wù)的系統(tǒng)不可用。用戶應(yīng)該檢查：

    是否有合適的Windows Sockets DLL文件在當(dāng)前路徑中。

    是否同時使用了多個WinSock實(shí)現(xiàn)。如果有多于一個的WINSOCK DLL在系統(tǒng)中，必須確保搜索路徑中第一個WINSOCK DLL文件是當(dāng)前加載的網(wǎng)絡(luò)子系統(tǒng)所需要的。

    查看WinSock實(shí)現(xiàn)的文檔以確保所有必須的部件都正確地安裝并配置好了。

 

WSATRY_AGAIN                    (11002)             Non-authoritative host not found.

此錯誤通常是在主機(jī)名解析時的臨時錯誤，它意味著本地服務(wù)器沒有從授權(quán)服務(wù)器接收到一個響應(yīng)。稍后的重試可能會獲得成功。

 

WSAVERNOTSUPPORTED     (10092)             WINSOCK.DLL version out of range.

當(dāng)前的WinSock實(shí)現(xiàn)不支持應(yīng)用程序指定的Windows Sockets規(guī)范版本。檢查是否有舊的Windows Sockets DLL文件正在被訪問。

 

WSAEDISCON                        (10101)             Graceful shutdown in progress.

由WSARecv()和WSARecvFrom()函數(shù)返回，指示遠(yuǎn)程方已經(jīng)初始化了一個“雅致”的關(guān)閉序列。

 

WSA_OPERATION_ABORTED   (OS dependent) Overlapped operation aborted.

     因?yàn)樘捉幼值年P(guān)閉，一個重疊操作被取消，或是執(zhí)行了WSAIoctl()函數(shù)的SIO_FLUSH命令。

以下英文解釋來自MSDN:

Error Codes

The following is a list of possible error codes returned by the WSAGetLastError call, along with their extended explanations. Errors are listed in alphabetical order by error macro. Some error codes defined in WINSOCK2.H are not returned from any function - these have not been listed here.

WSAEACCES

(10013)

Permission denied.

An attempt was made to access a socket in a way forbidden by its access permissions. An example is using a broadcast address for sendto without broadcast permission being set using setsockopt(SO_BROADCAST).

WSAEADDRINUSE

(10048)

Address already in use.

Only one usage of each socket address (protocol/IP address/port) is normally permitted. This error occurs if an application attempts to bind a socket to an IP address/port that has already been used for an existing socket, or a socket that wasn't closed properly, or one that is still in the process of closing. For server applications that need to bind multiple sockets to the same port number, consider using setsockopt(SO_REUSEADDR). Client applications usually need not call bind at all - connect will choose an unused port automatically. When bind is called with a wild-card address (involving ADDR_ANY), a WSAEADDRINUSE error could be delayed until the specific address is "committed." This could happen with a call to other function later, including connect, listen, WSAConnect or WSAJoinLeaf.

WSAEADDRNOTAVAIL

(10049)

Cannot assign requested address.

The requested address is not valid in its context. Normally results from an attempt to bind to an address that is not valid for the local machine. This can also result from connect, sendto, WSAConnect, WSAJoinLeaf, or WSASendTo when the remote address or port is not valid for a remote machine (e.g. address or port 0).

WSAEAFNOSUPPORT

(10047)

Address family not supported by protocol family.

An address incompatible with the requested protocol was used. All sockets are created with an associated "address family" (i.e. AF_INET for Internet Protocols) and a generic protocol type (i.e. SOCK_STREAM). This error will be returned if an incorrect protocol is explicitly requested in the socket call, or if an address of the wrong family is used for a socket, e.g. in sendto.

WSAEALREADY

(10037)

Operation already in progress.

An operation was attempted on a non-blocking socket that already had an operation in progress - i.e. calling connect a second time on a non-blocking socket that is already connecting, or canceling an asynchronous request (WSAAsyncGetXbyY) that has already been canceled or completed.

WSAECONNABORTED

(10053)

Software caused connection abort.

An established connection was aborted by the software in your host machine, possibly due to a data transmission timeout or protocol error.

WSAECONNREFUSED

(10061)

Connection refused.

No connection could be made because the target machine actively refused it. This usually results from trying to connect to a service that is inactive on the foreign host - i.e. one with no server application running.

WSAECONNRESET

(10054)

Connection reset by peer.

A existing connection was forcibly closed by the remote host. This normally results if the peer application on the remote host is suddenly stopped, the host is rebooted, or the remote host used a "hard close" (see setsockopt for more information on the SO_LINGER option on the remote socket.) This error may also result if a connection was broken due to "keep-alive" activity detecting a failure while one or more operations are in progress. Operations that were in progress fail with WSAENETRESET. Subsequent operations fail with WSAECONNRESET.

WSAEDESTADDRREQ

(10039)

Destination address required.

A required address was omitted from an operation on a socket. For example, this error will be returned if sendto is called with the remote address of ADDR_ANY.

WSAEFAULT

(10014)

Bad address.

The system detected an invalid pointer address in attempting to use a pointer argument of a call. This error occurs if an application passes an invalid pointer value, or if the length of the buffer is too small. For instance, if the length of an argument which is a struct sockaddr is smaller than sizeof(struct sockaddr).

WSAEHOSTDOWN

(10064)

Host is down.

A socket operation failed because the destination host was down. A socket operation encountered a dead host. Networking activity on the local host has not been initiated. These conditions are more likely to be indicated by the error WSAETIMEDOUT.

WSAEHOSTUNREACH

(10065)

No route to host.

A socket operation was attempted to an unreachable host. See WSAENETUNREACH

WSAEINPROGRESS

(10036)

Operation now in progress.

A blocking operation is currently executing. Windows Sockets only allows a single blocking operation to be outstanding per task (or thread), and if any other function call is made (whether or not it references that or any other socket) the function fails with the WSAEINPROGRESS error.

WSAEINTR

(10004)

Interrupted function call.

A blocking operation was interrupted by a call to WSACancelBlockingCall.

WSAEINVAL

(10022)

Invalid argument.

Some invalid argument was supplied (for example, specifying an invalid level to the setsockopt function). In some instances, it also refers to the current state of the socket - for instance, calling accept on a socket that is not listening.

WSAEISCONN

(10056)

Socket is already connected.

A connect request was made on an already connected socket. Some implementations also return this error if sendto is called on a connected SOCK_DGRAM socket (For SOCK_STREAM sockets, the to parameter in sendto is ignored), although other implementations treat this as a legal occurrence.

WSAEMFILE

(10024)

Too many open files.

Too many open sockets. Each implementation may have a maximum number of socket handles available, either globally, per process or per thread.

WSAEMSGSIZE

(10040)

Message too long.

A message sent on a datagram socket was larger than the internal message buffer or some other network limit, or the buffer used to receive a datagram into was smaller than the datagram itself.

WSAENETDOWN

(10050)

Network is down.

A socket operation encountered a dead network. This could indicate a serious failure of the network system (i.e. the protocol stack that the WinSock DLL runs over), the network interface, or the local network itself.

WSAENETRESET

(10052)

Network dropped connection on reset.

The connection has been broken due to "keep-alive" activity detecting a failure while the operation was in progress. It can also be returned by setsockopt if an attempt is made to set SO_KEEPALIVE on a connection that has already failed.

WSAENETUNREACH

(10051)

Network is unreachable.

A socket operation was attempted to an unreachable network. This usually means the local software knows no route to reach the remote host.

WSAENOBUFS

(10055)

No buffer space available.

An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full.

WSAENOPROTOOPT

(10042)

Bad protocol option.

An unknown, invalid or unsupported option or level was specified in a getsockopt or setsockopt call.

WSAENOTCONN

(10057)

Socket is not connected.

A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using sendto) no address was supplied. Any other type of operation might also return this error - for example, setsockopt setting SO_KEEPALIVE if the connection has been reset.

WSAENOTSOCK

(10038)

Socket operation on non-socket.

An operation was attempted on something that is not a socket. Either the socket handle parameter did not reference a valid socket, or for select, a member of an fd_set was not valid.

WSAEOPNOTSUPP

(10045)

Operation not supported.

The attempted operation is not supported for the type of object referenced. Usually this occurs when a socket descriptor to a socket that cannot support this operation, for example, trying to accept a connection on a datagram socket.

WSAEPFNOSUPPORT

(10046)

Protocol family not supported.

The protocol family has not been configured into the system or no implementation for it exists. Has a slightly different meaning to WSAEAFNOSUPPORT, but is interchangeable in most cases, and all Windows Sockets functions that return one of these specify WSAEAFNOSUPPORT.

WSAEPROCLIM

(10067)

Too many processes.

A Windows Sockets implementation may have a limit on the number of applications that may use it simultaneously. WSAStartup may fail with this error if the limit has been reached.

WSAEPROTONOSUPPORT

(10043)

Protocol not supported.

The requested protocol has not been configured into the system, or no implementation for it exists. For example, a socket call requests a SOCK_DGRAM socket, but specifies a stream protocol.

WSAEPROTOTYPE

(10041)

Protocol wrong type for socket.

A protocol was specified in the socket function call that does not support the semantics of the socket type requested. For example, the ARPA Internet UDP protocol cannot be specified with a socket type of SOCK_STREAM.

WSAESHUTDOWN

(10058)

Cannot send after socket shutdown.

A request to send or receive data was disallowed because the socket had already been shut down in that direction with a previous shutdown call. By calling shutdown a partial close of a socket is requested, which is a signal that sending or receiving or both has been discontinued.

WSAESOCKTNOSUPPORT

(10044)

Socket type not supported.

The support for the specified socket type does not exist in this address family. For example, the optional type SOCK_RAW might be selected in a socket call, and the implementation does not support SOCK_RAW sockets at all.

WSAETIMEDOUT

(10060)

Connection timed out.

A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

WSATYPE_NOT_FOUND

(10109)

Class type not found.

The specified class was not found.

WSAEWOULDBLOCK

(10035)

Resource temporarily unavailable.

This error is returned from operations on non-blocking sockets that cannot be completed immediately, for example recv when no data is queued to be read from the socket. It is a non-fatal error, and the operation should be retried later. It is normal for WSAEWOULDBLOCK to be reported as the result from calling connect on a non-blocking SOCK_STREAM socket, since some time must elapse for the connection to be established.

WSAHOST_NOT_FOUND

(11001)

Host not found.

No such host is known. The name is not an official hostname or alias, or it cannot be found in the database(s) being queried. This error may also be returned for protocol and service queries, and means the specified name could not be found in the relevant database.

WSA_INVALID_HANDLE

(OS dependent)

Specified event object handle is invalid.

An application attempts to use an event object, but the specified handle is not valid.

WSA_INVALID_PARAMETER

(OS dependent)

One or more parameters are invalid.

An application used a Windows Sockets function which directly maps to a Win32 function. The Win32 function is indicating a problem with one or more parameters.

WSAINVALIDPROCTABLE

(OS dependent)

Invalid procedure table from service provider.

A service provider returned a bogus proc table to WS2_32.DLL. (Usually caused by one or more of the function pointers being NULL.)

WSAINVALIDPROVIDER

(OS dependent)

Invalid service provider version number.

A service provider returned a version number other than 2.0.

WSA_IO_INCOMPLETE

(OS dependent)

Overlapped I/O event object not in signaled state.

The application has tried to determine the status of an overlapped operation which is not yet completed. Applications that use WSAGetOverlappedResult (with the fWait flag set to false) in a polling mode to determine when an overlapped operation has completed will get this error code until the operation is complete.

WSA_IO_PENDING

(OS dependent)

Overlapped operations will complete later.

The application has initiated an overlapped operation which cannot be completed immediately. A completion indication will be given at a later time when the operation has been completed.

WSA_NOT_ENOUGH_MEMORY

(OS dependent)

Insufficient memory available.

An application used a Windows Sockets function which directly maps to a Win32 function. The Win32 function is indicating a lack of required memory resources.

WSANOTINITIALISED

(10093)

Successful WSAStartup not yet performed.

Either the application hasn't called WSAStartup or WSAStartup failed. The application may be accessing a socket which the current active task does not own (i.e. trying to share a socket between tasks), or WSACleanup has been called too many times.

WSANO_DATA

(11004)

Valid name, no data record of requested type.

The requested name is valid and was found in the database, but it does not have the correct associated data being resolved for. The usual example for this is a hostname -> address translation attempt (using gethostbyname or WSAAsyncGetHostByName) which uses the DNS (Domain Name Server), and an MX record is returned but no A record - indicating the host itself exists, but is not directly reachable.

WSANO_RECOVERY

(11003)

This is a non-recoverable error.

This indicates some sort of non-recoverable error occurred during a database lookup. This may be because the database files (e.g. BSD-compatible HOSTS, SERVICES or PROTOCOLS files) could not be found, or a DNS request was returned by the server with a severe error.

WSAPROVIDERFAILEDINIT

(OS dependent)

Unable to initialize a service provider.

Either a service provider's DLL could not be loaded (LoadLibrary failed) or the provider's WSPStartup/NSPStartup function failed.

WSASYSCALLFAILURE

(OS dependent)

System call failure.

Returned when a system call that should never fail does. For example, if a call to WaitForMultipleObjects fails or one of the registry functions fails trying to manipulate theprotocol/namespace catalogs.

WSASYSNOTREADY

(10091)

Network subsystem is unavailable.

This error is returned by WSAStartup if the Windows Sockets implementation cannot function at this time because the underlying system it uses to provide network services is currently unavailable. Users should check:

• that the appropriate Windows Sockets DLL file is in the current path,
• that they are not trying to use more than one Windows Sockets implementation simultaneously. If there is more than one WINSOCK DLL on your system, be sure the first one in the path is appropriate for the network subsystem currently loaded.
• the Windows Sockets implementation documentation to be sure all necessary components are currently installed and configured correctly.

WSATRY_AGAIN

(11002)

Non-authoritative host not found.

This is usually a temporary error during hostname resolution and means that the local server did not receive a response from an authoritative server. A retry at some time later may be successful.

WSAVERNOTSUPPORTED

(10092)

WINSOCK.DLL version out of range.

The current Windows Sockets implementation does not support the Windows Sockets specification version requested by the application. Check that no old Windows Sockets DLL files are being accessed.

WSAEDISCON

(10094)

Graceful shutdown in progress.

Returned by WSARecv and WSARecvFrom to indicate the remote party has initiated a graceful shutdown sequence.

WSA_OPERATION_ABORTED

(OS dependent)

Overlapped operation aborted.

An overlapped operation was canceled due to the closure of the socket, or the execution of the SIO_FLUSH command in WSAIoctl.