Q.為何把檔案分成的最大塊數限制為10
A.近來發現有的使用者對於以為分成的塊數愈多速度就愈快，其實不然經過我和其他一些使用者的測試，有時更多的快數反而會使得速度下降，較多的快數只是對非常慢的連線有效。並且分成的快數越多，整個網路的負擔也越重，有可能導致網路（下載伺服器）崩潰。對於較慢的連線建議使用計劃下載的功能避開高峰時間（白天不能連線的站點，凌晨確能高速下載）

Q.出現"無法解析域名"的提示如何處理
A.應該是通過代理伺服器上網,參見問題"如何使用代理伺服器".

Q.為什麼下載到99%會速度會減慢甚至會暫停一段時間
A.下載接近完成的時候一般只剩下一兩個連線，由於其他連線的關閉，導致下載速度較慢，如果這一兩個連線再出現連線和下載線路不通暢，就會導致長時間的停頓，在快車中已就該情況進行了一些特殊處理，不過有時依然會有問題，可以設定超時時間為一個較小的值，可以改進一些，不過對正常的下載又有一些影響。最好不要理它，等一段時間就會下載完成。如果著急，可以手動停止再啟動。

Q.下載後的檔案無法開啟，提示“沒有關聯的程式”或者提示要用開啟方式
A.有三種可能性：
1.由於一些網站的限制或者使用者提交給快車下載的地址的錯誤，快車不能正確下載檔案，只是下載了一些頁面檔案，有時這些頁面是伺服器動態生成的，檔案字尾為php,asp等等，請參照常見問題解答中的相關問題答案確保快車可以下載到正確的檔案
2.沒有安裝處理下載的檔案的相關程式，比如字尾為zip的檔案，需要安裝解壓縮程式(WinZip等)
3.快車會給未下載完成的檔案新增.jc!的字尾，下載完成後會去掉該字尾，可能由於一些特殊的情況(安裝了某些實時病毒 監測軟體)造成無法自動完成該工作，請手動去掉已下載檔案的.jc!字尾。另外在選項/常規中去掉設定"新增字尾jc!直到 檔案下載完成"以後就不會有該問題。

Q.為何已經下載完的任務仍留在“正在下載”類別中，而並沒有自動移動到“已下載”類別中
A.請在選單/工具/預設下載屬性中修改類別屬性為"已下載",以後新增的任務下載完畢後會自動移動到“已下載”類別，當前已下載完畢而仍在“正在下載”類別中的任務可以託拽到“已下載”類別中。

Q.提示"Socket Error 100xx"
A.如果所有的站點均是如此,請確保你與Internet的連線沒有問題(如果使用代理伺服器請確保在快車中設定的正確，如果使用了防火牆也需要在防火牆軟體中設定允許快車訪問因特網，具體需要參閱防火牆軟體的幫助檔案)，另外也有可能是由於建立了過多的連線導致的，請不要同時下載太多的檔案。如果只是個別站點如此，應該是該站點臨時有點問題或者根本無法連線該站點（比如國內封掉了某些IP),請過些時候再試。

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) .Another possible reason for the WSAEACCES error is that when the bind function is called (on Windows NT 4 SP4 or later), another application, service, or kernel mode driver is bound to the same address with exclusive access. Such exclusive access is a new feature of Windows NT 4 SP4 and later, and is implemented by using the SO_EXCLUSIVEADDRUSE option.

WSAEADDRINUSE (10048) Address already in use . Typically, only one usage of each socket address (protocol/IP address/port) is 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 chooses an unused port automatically. When bind is called with a wildcard address (involving ADDR_ANY), a WSAEADDRINUSE error could be delayed until the specific address
is committed. This could happen with a call to another function later, including connect , listen , WSAConnect , or WSAJoinLeaf .

WSAEADDRNOTAVAIL (10049) Cannot assign requested address . The requested address is not valid in its context. This 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 (for example, 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 (that is, AF_INET for Internet Protocols) and a generic protocol type (that is, SOCK_STREAM). This error is 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, for example, in sendto .

WSAEALREADY (10037) Operation already in progress . An operation was attempted on a nonblocking socket with an operation already in progress—that is, calling connect a second time on a nonblocking 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 time-out 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—that is, one with no server application running.

WSAECONNRESET (10054) Connection reset by peer . An 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 uses 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 is 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 SOCKADDR structure, is smaller than the sizeof( SOCKADDR ).

WSAEHOSTDOWN (10064) Host is down . A socket operation failed because the destination host is 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—per- task or thread—to be outstanding, 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 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 (that is, the protocol stack that the Windows Sockets 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 nonsocket. 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 is 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. This message has a slightly different meaning from WSAEAFNOSUPPORT . However, it is interchangeable in most cases, and all Windows Sockets functions that return one of these messages also specify WSAEAFNOSUPPORT .

WSAEPROCLIM (10067) Too many processes. A Windows Sockets implementation may have a limit on the number of applications that can 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 have 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 the established connection failed because the 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 nonblocking sockets that cannot be completed immediately, for example recv when no data is queued to be read from the socket. It is a nonfatal error, and the operation should be retried later. It is normal for WSAEWOULDBLOCK to be reported as the result from calling connect on a nonblocking 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 host name 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 that 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 procedure 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 ersion 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, 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 that cannot be completed immediately. A completion indication will be given later when the operation has been completed.WSA_NOT_ENOUGH_MEMORY (OS dependent) Insufficient memory available. An application used a Windows Sockets function that 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 that the current active task does not own (that is, 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 host name-to-address translation attempt (using gethostbyname or WSAAsyncGetHostByName ) which uses the DNS (Domain Name Server). 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 nonrecoverable error. This indicates some sort of nonrecoverable error occurred during a database lookup. This may be because the database files (for example, 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 the protocol/name space 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) Nonauthoritative host not found. This is usually a temporary error during host name 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 (10101) Graceful shutdown in progress. Returned by WSARecv and WSARecvFrom to indicate that 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 .

檢視錯誤程式碼errno是除錯程式的一個重要方法。當linuc C api函式發生異常時,一般會將errno變數(需include errno.h)賦一個整數值, 不同的值表示不同的含義,可以通過檢視該值推測出錯的原因。在實際程式設計中用這一招解決了不少原本看來莫名其妙的問題。比較麻煩的是每次都要去linux原始碼裡面查詢錯誤程式碼的含義，現在把它貼出來，以後需要查時就來這裡看了。

以下來自linux 的核心程式碼中的/usr/include/asm/errno.h

#ifndef _I386_ERRNO_H

#define _I386_ERRNO_H

#define EPERM   1 /* Operation not permitted */

#define ENOENT   2 /* No such file or directory */

#define ESRCH   3 /* No such process */

#define EINTR   4 /* Interrupted system call */

#define EIO       5 /* I/O error */

#define ENXIO   6 /* No such device or address */

#define E2BIG   7 /* Arg list too long */

#define ENOEXEC   8 /* Exec format error */

#define EBADF   9 /* Bad file number */

#define ECHILD 10 /* No child processes */

#define EAGAIN 11 /* Try again */

#define ENOMEM 12 /* Out of memory */

#define EACCES 13 /* Permission denied */

#define EFAULT 14 /* Bad address */

#define ENOTBLK 15 /* Block device required */

#define EBUSY 16 /* Device or resource busy */

#define EEXIST 17 /* File exists */

#define EXDEV 18 /* Cross-device link */

#define ENODEV 19 /* No such device */

#define ENOTDIR 20 /* Not a directory */

#define EISDIR 21 /* Is a directory */

#define EINVAL 22 /* Invalid argument */

#define ENFILE 23 /* File table overflow */

#define EMFILE 24 /* Too many open files */

#define ENOTTY 25 /* Not a typewriter */

#define ETXTBSY 26 /* Text file busy */

#define EFBIG 27 /* File too large */

#define ENOSPC 28 /* No space left on device */

#define ESPIPE 29 /* Illegal seek */

#define EROFS 30 /* Read-only file system */

#define EMLINK 31 /* Too many links */

#define EPIPE 32 /* Broken pipe */

#define EDOM 33 /* Math argument out of domain of func */

#define ERANGE 34 /* Math result not representable */

#define EDEADLK         35      /* Resource deadlock would occur */
#define ENAMETOOLONG    36      /* File name too long */
#define ENOLCK          37      /* No record locks available */
#define ENOSYS          38      /* Function not implemented */
#define ENOTEMPTY       39      /* Directory not empty */
#define ELOOP           40      /* Too many symbolic links encountered */
#define EWOULDBLOCK     EAGAIN  /* Operation would block */
#define ENOMSG          42      /* No message of desired type */
#define EIDRM           43      /* Identifier removed */
#define ECHRNG          44      /* Channel number out of range */
#define EL2NSYNC        45      /* Level 2 not synchronized */
#define EL3HLT          46      /* Level 3 halted */
#define EL3RST          47      /* Level 3 reset */
#define ELNRNG          48      /* Link number out of range */
#define EUNATCH         49      /* Protocol driver not attached */
#define ENOCSI          50      /* No CSI structure available */
#define EL2HLT          51      /* Level 2 halted */
#define EBADE           52      /* Invalid exchange */
#define EBADR           53      /* Invalid request descriptor */
#define EXFULL          54      /* Exchange full */
#define ENOANO          55      /* No anode */
#define EBADRQC         56      /* Invalid request code */
#define EBADSLT         57      /* Invalid slot */

#define EDEADLOCK       EDEADLK

#define EBFONT          59      /* Bad font file format */
#define ENOSTR          60      /* Device not a stream */
#define ENODATA         61      /* No data available */
#define ETIME           62      /* Timer expired */
#define ENOSR           63      /* Out of streams resources */
#define ENONET          64      /* Machine is not on the network */
#define ENOPKG          65      /* Package not installed */
#define EREMOTE         66      /* Object is remote */
#define ENOLINK         67      /* Link has been severed */
#define EADV            68      /* Advertise error */
#define ESRMNT          69      /* Srmount error */
#define ECOMM           70      /* Communication error on send */
#define EPROTO          71      /* Protocol error */
#define EMULTIHOP       72      /* Multihop attempted */
#define EDOTDOT         73      /* RFS specific error */
#define EBADMSG         74      /* Not a data message */
#define EOVERFLOW       75      /* Value too large for defined data type */
#define ENOTUNIQ        76      /* Name not unique on network */
#define EBADFD          77      /* File descriptor in bad state */
#define EREMCHG         78      /* Remote address changed */
#define ELIBACC         79      /* Can not access a needed shared library */
#define ELIBBAD         80      /* Accessing a corrupted shared library */
#define ELIBSCN         81      /* .lib section in a.out corrupted */
#define ELIBMAX         82      /* Attempting to link in too many shared libraries */
#define ELIBEXEC        83      /* Cannot exec a shared library directly */
#define EILSEQ          84      /* Illegal byte sequence */
#define ERESTART        85      /* Interrupted system call should be restarted */
#define ESTRPIPE        86      /* Streams pipe error */
#define EUSERS          87      /* Too many users */
#define ENOTSOCK        88      /* Socket operation on non-socket */
#define EDESTADDRREQ    89      /* Destination address required */
#define EMSGSIZE        90      /* Message too long */
#define EPROTOTYPE      91      /* Protocol wrong type for socket */
#define ENOPROTOOPT     92      /* Protocol not available */
#define EPROTONOSUPPORT 93      /* Protocol not supported */
#define ESOCKTNOSUPPORT 94      /* Socket type not supported */
#define EOPNOTSUPP      95      /* Operation not supported on transport endpoint */
#define EPFNOSUPPORT    96      /* Protocol family not supported */
#define EAFNOSUPPORT    97      /* Address family not supported by protocol */
#define EADDRINUSE      98      /* Address already in use */
#define EADDRNOTAVAIL   99      /* Cannot assign requested address */
#define ENETDOWN        100     /* Network is down */
#define ENETUNREACH     101     /* Network is unreachable */
#define ENETRESET       102     /* Network dropped connection because of reset */
#define ECONNABORTED    103     /* Software caused connection abort */
#define ECONNRESET      104     /* Connection reset by peer */
#define ENOBUFS         105     /* No buffer space available */
#define EISCONN         106     /* Transport endpoint is already connected */
#define ENOTCONN        107     /* Transport endpoint is not connected */
#define ESHUTDOWN       108     /* Cannot send after transport endpoint shutdown */
#define ETOOMANYREFS    109     /* Too many references: cannot splice */
#define ETIMEDOUT       110     /* Connection timed out */
#define ECONNREFUSED    111     /* Connection refused */
#define EHOSTDOWN       112     /* Host is down */
#define EHOSTUNREACH    113     /* No route to host */
#define EALREADY        114     /* Operation already in progress */
#define EINPROGRESS     115     /* Operation now in progress */
#define ESTALE          116     /* Stale NFS file handle */
#define EUCLEAN         117     /* Structure needs cleaning */
#define ENOTNAM         118     /* Not a XENIX named type file */
#define ENAVAIL         119     /* No XENIX semaphores available */
#define EISNAM          120     /* Is a named type file */
#define EREMOTEIO       121     /* Remote I/O error */
#define EDQUOT          122     /* Quota exceeded */

#define ENOMEDIUM       123     /* No medium found */
#define EMEDIUMTYPE     124     /* Wrong medium type */
#define ECANCELED       125     /* Operation Canceled */
#define ENOKEY          126     /* Required key not available */
#define EKEYEXPIRED     127     /* Key has expired */
#define EKEYREVOKED     128     /* Key has been revoked */
#define EKEYREJECTED    129     /* Key was rejected by service */

/* for robust mutexes */
#define EOWNERDEAD      130     /* Owner died */
#define ENOTRECOVERABLE 131     /* State not recoverable */

#endif