Bad File Descriptor with Linux Socket write Bad File Descriptor C

Question

I have an interesting problem with write 2  function  PrepareResponseForSetCoordinates function causes bad file descriptor error on write   Here is the line of error  perror  ERROR writing to socket    total output  ERROR writing to socket  Bad file descriptor  I am sure that I have established the connection because PrepareResponseForConnectionTest works like a charm   Can you have any idea about the reason of the error   When I use gcc as compiler there was no problem  After that because of using multiple new cpp sources I am using g   as compiler and I have this error   Regards  Here below my code    define MAX PMS MESSAGE LEN  4096  unsigned char baCommBuffer MAX PMS MESSAGE LEN   unsigned char PrepareResponseForSetCoordinates void        unsigned char baTempBuff 255   0       unsigned short bCnt 0 i 0 bCsum 0 bCnt2 0  time t lEpochTime  time t lSessionTime   memset baTempBuff 0 sizeof baTempBuff    memset baCommBuffer 0 sizeof baCommBuffer    bzero baCommBuffer MAX PMS MESSAGE LEN   bzero baTempBuff sizeof baTempBuff      lEpochTime   time NULL   baCommBuffer bCnt           START CHAR  baCommBuffer bCnt           START CHAR  baCommBuffer bCnt           PACKET SEPERATOR  sprintf  char  baTempBuff   ld   unsigned long lEpochTime   memcpy baCommBuffer bCnt baTempBuff 10    bzero baTempBuff sizeof baTempBuff    bCnt  10  baCommBuffer bCnt           PACKET SEPERATOR      lSessionTime   time NULL   if SPMSMessage lSessionID  lSessionTime   SPMSMessage lSessionID   else lSessionTime lEpochTime  sprintf  char  baTempBuff   ld   unsigned long lSessionTime   memcpy baCommBuffer bCnt baTempBuff 10   bzero baTempBuff sizeof baTempBuff    bCnt  10  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt           PMC ID  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt           PMS ID  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            R   baCommBuffer bCnt            E   baCommBuffer bCnt            P   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            C   baCommBuffer bCnt            O   baCommBuffer bCnt            O   baCommBuffer bCnt            S   baCommBuffer bCnt           PACKET SEPERATOR  if SPMSMessage bParam   SET COOR CAM1 PARAM    baCommBuffer bCnt            2   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            O   baCommBuffer bCnt            N   baCommBuffer bCnt            E   baCommBuffer bCnt           PARAMETER SEPERATOR  baCommBuffer bCnt            A   baCommBuffer bCnt            C   baCommBuffer bCnt            K     else if SPMSMessage bParam   SET COOR CAM2 PARAM    baCommBuffer bCnt            2   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            T   baCommBuffer bCnt            W   baCommBuffer bCnt            O   baCommBuffer bCnt           PARAMETER SEPERATOR  baCommBuffer bCnt            A   baCommBuffer bCnt            C   baCommBuffer bCnt            K         else   baCommBuffer bCnt            1   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            N   baCommBuffer bCnt            A   baCommBuffer bCnt            C   baCommBuffer bCnt            K             baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt                memset baTempBuff 0 sizeof baTempBuff    bCsum   CalculateCheckSum baCommBuffer   sprintf  char  baTempBuff    2X  bCsum   memcpy baCommBuffer bCnt baTempBuff 2   bzero baTempBuff sizeof baTempBuff    bCnt  2  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt           END CHAR  baCommBuffer bCnt           END CHAR    ifdef  DEBUG DEEP DETAILED             if EDebugDeepDetail lt GetDebugLevelOfPMC                                      printf  WILL BE sent   s uzunluk  d n   baCommBuffer bCnt                       sprintf caLogStr  WILL BE sent   s uzunluk  d n   baCommBuffer bCnt                       PrintToLogFile caLogStr                       memset caLogStr 0 MAX LOG STRLEN                      endif          if  ETcpConnectionState   ETcpStateConnected      ETcpConnectionState   ETcpStateConnectedAndWaitingToWrite                           if  write sockfd baCommBuffer bCnt   lt  0                                 ifdef  DEBUG DETAILED                 if EDebugDetail lt GetDebugLevelOfPMC                                           perror  ERROR writing to socket                          PrintToLogFile  ERROR writing to socket                                          endif              return 0                                 ifdef  DEBUG DEEP DETAILED                 if EDebugDeepDetail lt GetDebugLevelOfPMC                                          printf  sent   s uzunluk  d n   baCommBuffer bCnt                       sprintf caLogStr  sent   s uzunluk  d n   baCommBuffer bCnt                       PrintToLogFile caLogStr                       memset caLogStr 0 MAX LOG STRLEN                                      endif                   else                            ifdef  DEBUG DETAILED                     if EDebugDetail lt GetDebugLevelOfPMC                                              PrintToLogFile  Hen  z Baglanti Yok n                                           endif                 return 0              return  bCnt          Here below you can see the code which run without error   unsigned char PrepareResponseForConnectionTest void     unsigned char baTempBuff 20   0   unsigned char bCnt 0 i 0 bCsum 0  time t lEpochTime  time t lSessionTime   memset baTempBuff 0 sizeof baTempBuff    memset baCommBuffer 0 sizeof baCommBuffer    bzero baCommBuffer MAX PMS MESSAGE LEN   bzero baTempBuff sizeof baTempBuff      lEpochTime   time NULL   baCommBuffer bCnt           START CHAR  baCommBuffer bCnt           START CHAR  baCommBuffer bCnt           PACKET SEPERATOR  sprintf  char  baTempBuff   ld   unsigned long lEpochTime   memcpy baCommBuffer bCnt baTempBuff 10    bzero baTempBuff sizeof baTempBuff    bCnt  10  baCommBuffer bCnt           PACKET SEPERATOR   lSessionTime   SPMSMessage lSessionID   sprintf  char  baTempBuff   ld   unsigned long lSessionTime   memcpy baCommBuffer bCnt baTempBuff 10   bzero baTempBuff sizeof baTempBuff    bCnt  10  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt           PMC ID  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt           PMS ID  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            R   baCommBuffer bCnt            E   baCommBuffer bCnt            P   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            C   baCommBuffer bCnt            O   baCommBuffer bCnt            N   baCommBuffer bCnt            T   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            1   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt            A   baCommBuffer bCnt            C   baCommBuffer bCnt            K   baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt                memset baTempBuff 0 sizeof baTempBuff    bCsum   CalculateCheckSum baCommBuffer   sprintf  char  baTempBuff    2X  bCsum   memcpy baCommBuffer bCnt baTempBuff 2   bzero baTempBuff sizeof baTempBuff    bCnt  2  baCommBuffer bCnt           PACKET SEPERATOR  baCommBuffer bCnt           END CHAR  baCommBuffer bCnt           END CHAR             if  ETcpConnectionState   ETcpStateConnected      ETcpConnectionState   ETcpStateConnectedAndWaitingToWrite                           if  write sockfd baCommBuffer bCnt   lt  0                             perror  ERROR writing to socket n                 PrintToLogFile  ERROR writing to socket n                                   ifdef  DEBUG DEEP DETAILED                 if EDebugDeepDetail lt GetDebugLevelOfPMC                                          printf  sent   s uzunluk  d n   baCommBuffer bCnt                       sprintf caLogStr  sent   s uzunluk  d n   baCommBuffer bCnt                       PrintToLogFile caLogStr                       memset caLogStr 0 MAX LOG STRLEN                                      endif                 return 0                    else                            ifdef  DEBUG DETAILED                     if EDebugDetail lt GetDebugLevelOfPMC                                              PrintToLogFile  There is no connection yet n                                           endif                   return 0                       printf   n n    return  bCnt       Here is my InitializeConnection function and ConnectToServer function   void InitializeTcpConnection int argc  char  argv         int optval     socklen t optlen   sizeof optval   ETcpConnectionState   ETcpStateNotConnected      if  argc  lt  3                fprintf stderr  usage   s hostname or ip port n   argv 0            ifdef  DEBUG PROCESS        if EDebugProcess lt GetDebugLevelOfPMC                     sprintf caLogStr  usage   s hostname or ip port n   argv 0            PrintToLogFile caLogStr           memset caLogStr 0 MAX LOG STRLEN                     endif        exit 0             portno   atoi argv 2           int socket domain type protocol         socket creates an endpoint for communication and returns a descriptor        AF INET  ARPA Internet protocols        SOCK STREAM  sequenced  two way connection based byte streams                return  Socket returns a non-negative descriptor on success         On failure it returns -1 and sets errno to indicate the error               sockfd   socket AF INET  SOCK STREAM  0       if  sockfd  lt  0             ifdef  DEBUG PROCESS         if EDebugProcess lt GetDebugLevelOfPMC                      perror  ERROR creating socket            PrintToLogFile  ERROR creating socket n                        endif         exit 1                           Set the option active       optval   1     optlen   sizeof optval      if setsockopt sockfd  SOL SOCKET  SO KEEPALIVE   amp optval  optlen   lt  0               ifdef  DEBUG PROCESS       if EDebugProcess lt GetDebugLevelOfPMC                        perror  setsockopt                PrintToLogFile  ERROR creating socket n                     endif       close sockfd         exit EXIT FAILURE            ifdef  DEBUG PROCESS    if EDebugProcess lt GetDebugLevelOfPMC             printf  SO KEEPALIVE set on socket n        PrintToLogFile  SO KEEPALIVE set on socket n                 endif       Check the status again       if getsockopt sockfd  SOL SOCKET  SO KEEPALIVE   amp optval   amp optlen   lt  0            ifdef  DEBUG PROCESS        if EDebugProcess lt GetDebugLevelOfPMC                       perror  getsockopt                PrintToLogFile  getsockopt                     endif       close sockfd         exit EXIT FAILURE            ifdef  DEBUG PROCESS    if EDebugProcess lt GetDebugLevelOfPMC            printf  SO KEEPALIVE is  s n    optval    ON     OFF              endif      ifdef  DEBUG PROCESS      if EDebugProcess lt GetDebugLevelOfPMC              PrintToLogFile  Setting socket for reusability n              endif     if  setsockopt sockfd  SOL SOCKET  SO REUSEADDR   amp optval  sizeof int      -1                ifdef  DEBUG PROCESS        if EDebugProcess lt GetDebugLevelOfPMC                             perror  setsockopt                    PrintToLogFile  Setting socket option error n                     endif                 exit 1                               get the address info by either host name or IP address     SetTcpServerIpAddress argv 1        server   gethostbyname argv 1        if  server    NULL                  ifdef  DEBUG PROCESS         if EDebugProcess lt GetDebugLevelOfPMC                      PrintToLogFile  ERROR  no such host n                       endif         exit 1              bzero  char     amp serv addr  sizeof serv addr        serv addr sin family   AF INET      bcopy  char   server- gt h addr   char    amp serv addr sin addr s addr  server- gt h length         serv addr sin port  unsigned short        htons converts the unsigned short hostshort from host byte order to network byte order     serv addr sin port   htons portno         ETcpConnectionState   ETcpStateWaitingForConnection      int ConnectToServer void                        if  connect sockfd  struct sockaddr     amp serv addr sizeof serv addr    lt  0                                                   ifdef  DEBUG DETAILED                         if EDebugDetail lt GetDebugLevelOfPMC                                                      PrintToLogFile  ERROR connecting                                                       endif                         return 1     connection error                           exit 1                                             else                                                ifdef  DEBUG DETAILED                         if EDebugDetail lt GetDebugLevelOfPMC                                                      PrintToLogFile  connection established n                                                       endif                      ifndef PMS COMM POLL MODE                          ifdef  DEBUG DETAILED                         if EDebugDetail lt GetDebugLevelOfPMC                                                      PrintToLogFile  State is non poll mode n                                                       endif                     ETcpConnectionState   ETcpStateConnected                       endif                      ifdef PMS COMM POLL MODE                          ifdef  DEBUG DETAILED                         if EDebugDetail lt GetDebugLevelOfPMC                                                      PrintToLogFile  State is poll mode n                                                        endif                     ETcpConnectionState   ETcpStateConnectedAndWaitingToRead                       endif                      SendRequestToGetImageUploadInfo                          return 0

User · Answer

The value you have passed as the file descriptor is not valid. It is either negative or does not represent a currently open file or socket.

So you have either closed the socket before calling write() or you have corrupted the value of 'sockfd' somewhere in your code.

It would be useful to trace all calls to close(), and the value of 'sockfd' prior to the write() calls.

Your technique of only printing error messages in debug mode seems to me complete madness, and in any case calling another function between a system call and perror() is invalid, as it may disturb the value of errno. Indeed it may have done so in this case, and the real underlying error may be different.

User · Answer

In general  when  Bad File Descriptor  is encountered  it means that the socket file descriptor you passed into the API is not valid  which has multiple possible reasons    The fd is already closed somewhere  The fd has a wrong value  which is inconsistent with the value obtained from socket   api

User · Answer

I had this error too  my problem was in some part of code I didn t close file descriptor and in other part  I tried to open that file   use close fd  system call after you finished working on a file

[c] Bad File Descriptor with Linux Socket write() Bad File Descriptor C

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