Packet-radio.net

Programming technics for servers.

 The servers are exec programs (.COM or .EXE). They are compact and fast.
They will work as the function of the messages which are addressed to them.

 They should be compact because the available memory to run their application
is limited (check the information Ok:nnnn in the status window). They should
be fast because they are executed in the MsDos environment which is not
multi-task.

 The programming language can be of any kind provided that it could be
compiled and that it is able to read parameters which are given appended in
the command line.

 I wrote three servers in TurboC but I have no equivalent in TurboPascal or
in TurboBasic, since I usually don't write in these languages. The working
principle remains always the same whatever language is utilized.

 The program is called with the following manner from the MsDos (Example for
the REQDIR.COM command) :

 C> REQDIR.COM TEMP.$$$

 TEMP.$$$ is the name of the file in which the message addressed to REQDIR is
located. It is necessary to read the name of this file in the command line,
as the one can change from one call to another.

 The file TEMP.$$$ contains the message with the following format :

 SP REQDIR < F6FBB
 Title of message
 Text of message line 1
 Text of message line 2
 ...
 Text of message last line.
 /EX

 The server should then eventually work as a function of the contents of this
message.

 The server can read and make use of the configuration file of the BBS
software (in particular INIT.SRV) to execute its process.

 If the server generates a return message, it should be APPENDED to the
incoming mail file to the BBS. The name of this file can be found in
INIT.SRV. Take care : it is necessary to open the incoming mail file in
APPEND as to add the answer at the end of the file. If it is not done this
way, the messages which could be waiting in this file are destroyed.

 The incoming mail file is tested each and every minute, except in the case
of the usage of a service, where it is tested right after.

 The format of the messages in the incoming mail file is identical to the
format of the file given to the server. Several messages can be written
sequentially in the file. There should not be blank lines or separations
between the messages. The routing fields (@ field), and the originator (<
field) should mandatory be specified. The originator field is the callsign of
the BBS which is taken from the INIT.SRV file.


 Example of server REQFIL written in C language.

/*
 * REQFIL.C Server example.
 *
 * This server is called with a command line like this :
 *
 * REQFIL.COM FILE
 *
 * FILE is the filename of the message to be answered.
 *
 *
 * This server answers to a message like this :
 *
 * SP REQFIL < FC1EBN
 * TEST.TXT @ F6ABJ
 * Text is not necessary
 * /EX
 *
 * by a message like this
 *
 * # <- This is a local message
 * SP FC1EBN @ F6ABJ < F6FBB <- command line
 * Req File : TEST.TXT <- subject
 * Contents of the file <- text
 * etc.....
 * /EX <- end of text (must be in 1st column)
 *
 * Appent to mail in bbs file.
 *
 *
 * The server receives from FBB software 1 argument :
 *
 * argv[1] = Name of the file including the message received from
 * FBB software.
 *
 * ============================================
 * The server must APPEND its answer to MAIL.IN
 * file to avoid destroying existing mail.
 * ============================================
 *
 * As this server opens the INIT.SRV file, it must be in the same
 * directory.
 *
 */

 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/stat.h>

 /* Offsets of parameters from INIT.SRV */

 #define BBS_CALL 1
 #define USER_DIR 8
 #define MAIL_IN 14

 main(int argc, char **argv)
 {
 #define LINE 80
   int end = 0;
   int index = 0;
   FILE *fptr;
   char buffer[LINE];
   char sender[LINE];
   char route[LINE];
   char file[LINE];
   char bbs_call[LINE];
   char base_dir[LINE];
   char mail_in[LINE];

   if (argc != 2) exit(1);            /* Check the number of arguments */

   /* The first task is to open and then read the message */

   fptr = fopen(argv[1], "rt") ;      /* Open the received message */
   if (fptr == NULL) exit(1);

   fgets(buffer, LINE, fptr);         /* Read the command line */
   sscanf(buffer, "%*s %*s %*s %s\n", sender);

   *file = *route = '\0';
   fgets(buffer, LINE, fptr);         /* Read the subject */
   strupr(buffer);                    /* Capitalize */

   /* Scan dir and route */
   sscanf(buffer, "%[^@\n]%[^\n]", file, route);

   fclose(fptr);                   /* All needed is read in the message */

   /* We must get some informations from the INIT.SRV file */

   fptr = fopen("INIT.SRV", "rt"); /* Open the file */
   if (fptr == NULL) exit(1);

   /* Scan the file to get the requested lines. */
   while (!end) {
     fgets(buffer, LINE, fptr) ;
     if (*buffer == '#') continue; /* Comments ignored */

     switch (++index) {

     case BBS_CALL:
       sscanf(buffer,"%[0-9A-Za-z]", bbs_call);
       break; /* Callsign */

     case USER_DIR:
       sscanf(buffer,"%s\n", base_dir);
       break; /* Users directory */

     case MAIL_IN :
       sscanf(buffer,"%s\n", mail_in);
       end = 1; /* Mail in file */
       break;

     }
   }

   fclose(fptr);

   /* Append the answer to mail in file */
   /* Mail in file is opened in appent text mode */

   if (fptr = fopen(mail_in, "at")) {

     /* Tell that this is a message from this BBS */

     fprintf(fptr, "#\n");

     /* Send command line */
     fprintf(fptr, "SP %s %s < %s\n",
     sender, route, bbs_call);

     /* Send subject and requested file */
     send_file(fptr, base_dir, file);

     /* Send end of message */
     fprintf(fptr, "/EX\n");

     /* That's all ! */
     fclose(fptr);
   }
   exit(0);                                /* Tell BBS all is correct */
 }

 int points(char *ptr)   /* Looks for a ".." sequence in the path */
 {
   while (*ptr) {
     if ((*ptr == '.') && (*(ptr+1) == '.')) return(1);
     ++ptr;
   }
   return(0);          /* ".." not fond ! */
 }

 send_file(FILE *fptr, char *base_dir, char *filename)
 {
 #define BUF_SIZE 1000
   int fd;
   int nb;
   char path[256];
   char buffer[BUF_SIZE];
   char last_char;

   sprintf(path, "%s%s", base_dir, filename);       /* Complete path */

   fprintf(fptr, "ReqFil 1.1 : %s\n", filename);       /* Subject */

   if ((!points(path)) && ((fd = open(path, O_RDONLY | O_TEXT)) != -1)) {
     while (nb = read(fd, buffer, BUF_SIZE)) {
       fwrite(buffer, nb, 1, fptr);
       last_char = buffer[nb-1];
     }
     close(fd);

     /* Be sure /EX will be in first column */
     if (last_char != '\n') fputc('\n', fptr);

   }
   else fprintf(fptr, "File not found !\n");
 }