[9fans] dial M for Minimalism

forsyth@caldo.demon.co.uk wrote:

> as a doctor, i am often asked ``why doesn't Plan 9 (or Inferno) use
> the `standard' socket calls?''
>
> the source of tcpblast.c was recently posted to this list.
> it makes a tcp/ip call to a given machine.
> the bits that do so are shown below (i have completed
> the code that looks up the service name):
>
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> #include <netdb.h>
>
>         ...
>
> struct sockaddr_in sock_in;
> struct servent *sp;
> struct hostent *host;
>
>         ...
>  memset(&sock_in, 0, sizeof (sock_in));
>  sock_in.sin_family = AF_INET;
>  f = socket(AF_INET, SOCK_STREAM, 0);
>  if (f < 0) {
>   perror("tcpblast: socket");
>   exit(3);
>  }
>  if (bind(f, (struct sockaddr*) &sock_in, sizeof (sock_in)) < 0) {
>   perror("tcpblast: bind");
>   exit(1);
>  }
>
>  host = gethostbyname(argv[1]);
>  if (host) {
>   sock_in.sin_family = host->h_addrtype;
>   memmove(&sock_in.sin_addr, host->h_addr, host->h_length);
>  } else {
>   sock_in.sin_family = AF_INET;
>   sock_in.sin_addr.s_addr = inet_addr(argv[1]);
>   if (sock_in.sin_addr.s_addr == -1) {
>    fprintf(stderr, "tcpblast: %s unknown host\n", argv[1]);
>    exit(1);
>   }
>  }
>  sp = getservbyname("discard", "tcp");
>  if (sp)
>    sock_in.sin_port = sp->s_port;
>  else
>    sock_in.sin_port = htons(9);
>
>  if (connect(f, (struct sockaddr*) &sock_in, sizeof(sock_in)) <0)
>  {
>   perror("tcpblast connect:");
>   exit(1);
>  }
>
> by contrast, in my variant for Plan 9, i wrote:
>
> #include <u.h>
> #include <libc.h>
>
>         ...
>
>         fd = dial(netmkaddr(argv[0], "tcp", "discard"), nil, nil, nil);
>         if(fd < 0){
>                 fprint(2, "tcpbuzz: can't dial %s: %r\n", argv[0]);
>                 exits("dial");
>         }
>
> the nil, nil, nil looks and sounds like a Eurovision Song Contest
> score, which is perhaps a blemish.  (each nil represents a default
> that more specialised applications can set to access such things as
> port number assignment and the connection's control and status files.
> Inferno's dial interface is simpler still, partly because of the use
> of Limbo tuples.)  apart from that, the incantation is straightforward
> and easy to write.  because the interface and underlying
> infrastructure provides a good degree of abstraction, it also works
> without change for all suitable network types and protocols; it isn't
> limited to TCP/IP or IP networks.  the connection service and name
> space together sort out the details; that the network files live in
> the per-process name space also enables the same code to dial through
> an imported gateway.