Review of Donahoo Chapter 2,3,4 (TCP sockets, Addressing/naming services, UDP sockets.  This book presents very basic examples  of  sockets programs written in "C".

 The UDPEcho code is here: https://people.cs.clemson.edu/~jmarty/courses/CPSC6240-Student/code/UDPEcho/
 The TCPEcho code is here:  https://people.cs.clemson.edu/~jmarty/courses/CPSC6240-Student/code/TCPEcho/

• Ch2 assumes address parameters passed to client programs are address numbers (i.e., dotted quad notation for V4).
• It shows how to deal with V6 programs .... but to best support V4 and V6 use the Address Naming Service approach described in Ch3.
• Socket addresses:
  • Generic struct :
    • struct sockaddr
  • IP V4 version - two parts.
    • struct in_addr
      • uint32_t s_addr; 4 octets
    • struct sockaddr_in
      • ....struct in_addr sin_addr ; the actual IP V4 address, 4 octets
      • ....
  • IP V6 : NOTE: I believe p.24 of the second edition of Donahoo has a typo...the IPV6 structs should be:
    • struct in6_addr
      • uint8_t s_addr[16] : IPV6 address is 16 octets
    • struct sockaddr_in6
      • ...struct in6_addr sin6_addr;
      • ...
• Routines for converrting string Address numbers to binary addresses - examples below assume IP V6 addresses
  • int inet_pton(int addressFamily, const char *src, void *dst)
    • Printable to numeric
    • Need to know if it's AF_INET or AF_INET6),
    • Caller provides string in src ptr
    • Result is placed in callers memory pointed to by dst.
      • Caller can allocate memory to hold the largest possible string name for IPV6 address number:
        • char str[INET6_ADDRSTRLEN];\
        • struct sockaddr_storage myAddress; //the system ensures this is large enough
        • Caller invokes: inet_pton(AF_INET6,(char *)str, (void *)&myAddress;
  • int inet_ntop(int addressFamily,const void *src, char *dst, socklen_t dstBytes);
    • Numeric to printable
    • caller's IP V6 address (struct in6_addr sin6_addr) is pointed to by the src ptr
    • The returned printable address number (string) is returned in the callers dst ptr (or up to dstBytes - the caller indicates the size of its string buffer
    • The client can allocate the string buffer using:
      • char str[INET6_ADDRSTRLEN];\

Last update: 3/13/2019