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Midterm Test #1 Answers
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- Ian! D. Allen - idallen@idallen.ca - www.idallen.com

Test #1 Written Answer Section - Points: 50  (12 of 20%)

Read both sides!  Closed book.  No aids.  No electronic devices.

  1.   [Points: 1] Give the dotted-quad network mask for
       this subnet: 10.2.100.0/26   255.255.255.192

  2.   [Points: 2] What is the next sub-net address
       numerically greater than: 6.7.8.0/25?  6.7.8.128/25

  3.   [Points: 2] What is the next sub-net address
       numerically greater than: 2.3.4.0/24?  2.3.5.0/24

  4.   [Points: 1] Which Unix file name is used to map port
       name "smtp" into port number 25?  /etc/services

  5.   [Points: 6] TCP/UDP port numbers are divided into
       named ranges by ICANN/IANA.  Give the IANA name for
       each range and give the port start and end values of
       the range.  see http://www.iana.org/assignments/port-numbers

  6.   [Points: 1] Correct this non-portable line of code:
       saddr.sin_port=portno;  =htons(portno)

  7.   [Points: 1] Correct this non-portable line of code:
       serv_addr.sin_addr.s_addr=INADDR_ANY;  =htonl(INADDR_ANY)

  8.   [Points: 4] Give any two of the three RFC1918 private
       address space blocks and masks.
       10/8 255.0.0.0 172.16/12 255.240.0.0 192.168/16 255.255.0.0

  9.   [Points: 3] List in execution order the two major
       Unix/Linux network system call function names used in
       a TCP client (e.g. your client.c):  socket,connect

  10.  [Points: 5] List in execution order the four major
       Unix/Linux network system call function names used in
       a TCP server (e.g. your server2.c):  socket,bind,listen,accept

  11.  [Points: 1] Give a C library function call that will
       send a signal to terminate the program after 30
       minutes (e.g. as used in server2.c):  alarm(30*60)

  12.  [Points: 1] In a memory dump that shows bytes
       numbered in ascending order from left-to-right on the
       page, which Endian order shows multi-byte quantities
       as written "backwards" ?  Little

  13.  [Points: 2] Give the dotted-quad form for the IP
       address represented by the bit pattern -1.  255.255.255.255

  14.  [Points: 1] What Unix command shows the MAC, IP
       address, and network mask of each network interface? ifconfig

  15.  [Points: 13] Write the detailed PDL for any process
       loop (just the loop!) that wishes to read data from
       one file descriptor and write it to another
       descriptor.

    WHILE 1
       numread = READ some data from input unit into fixed buffer
       IF numread < 0 THEN print error message and break loop  /* (1) */
       IF numread == 0 THEN print EOF message and break loop   /* (2) */
       ASSERT( numread > 0 )      /* man 3 assert */
       numwrite = WRITE numread bytes from buffer to output unit
       IF numwrite < 0 THEN print error message and break loop /* (3) */
    END WHILE

  16.  [Points: 6] Explain in detail which conditions will
       terminate (break) the above loop.

       break on read error (nr < 0) from input descriptor
       break on EOF (nr == 0) from input descriptor
       break on write error (nw < 0) to output descriptor