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NAME
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dial, announce, listen, accept, reject, netmkaddr, dialparse –
make and break network connections
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SYNOPSIS
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#include <u.h>
#include <libc.h>
int dial(char *addr, char *local, char *dir, int *cfdp)
int announce(char *addr, char *dir)
int listen(char *dir, char *newdir)
int accept(int ctl, char *dir)
int reject(int ctl, char *dir, char *cause)
char* netmkaddr(char *addr, char *defnet, char *defservice)
int dialparse(char *addr, char **net, char **unix,
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DESCRIPTION
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For these routines, addr is a network address of the form network!netaddr!service,
network!netaddr, or simply netaddr. Network is tcp, udp, unix,
or the special token, net. Net is a free variable that stands
for any network in common between the source and the host netaddr.
Netaddr can be a host name, a
domain name, or a network address.
On Plan 9, the dir argument is a path name to a line directory
that has files for accessing the connection. To keep the same
function signatures, the Unix port of these routines uses strings
of the form /dev/fd/n instead of line directory paths. These strings
should be treated as opaque data and ignored.
Dial makes a call to destination addr on a multiplexed network.
If the network in addr is net, dial will try in succession all
networks in common between source and destination until a call
succeeds. It returns a file descriptor open for reading and writing
the data file in the line directory. The addr file in the line
directory contains the address called. Dial’s local, dir, and
cfdp arguments are not supported and must be zero.
Announce and listen are the complements of dial. Announce establishes
a network name to which calls can be made. Like dial, announce
returns an open ctl file. The netaddr used in announce may be
a local address or an asterisk, to indicate all local addresses,
e.g. tcp!*!echo. The listen routine takes as its
first argument the dir of a previous announce. When a call is
received, listen returns an open ctl file for the line the call
was received on. It sets newdir to the path name of the new line
directory. Accept accepts a call received by listen, while reject
refuses the call because of cause. Accept returns a file descriptor
for
the data file opened ORDWR.
Netmkaddr makes an address suitable for dialing or announcing.
It takes an address along with a default network and service to
use if they are not specified in the address. It returns a pointer
to static data holding the actual address to use.
Dialparse parses a network address as described above into a network
name, a Unix domain socket address, an IPv4 host address, and
an IPv4 port number.
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EXAMPLES
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Make a call and return an open file descriptor to use for communications:
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int callkremvax(void)
{
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return dial("kremvax", 0, 0, 0);
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}
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Connect to a Unix socket served by acme(4):
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int dialacme(void)
{
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return dial("unix!/tmp/ns.ken.:0/acme", 0, 0, 0);
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}
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Announce as kremvax on TCP/IP and loop forever receiving calls
and echoing back to the caller anything sent:
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int
bekremvax(void)
{
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int dfd, acfd, lcfd;
char adir[40], ldir[40];
int n;
char buf[256];
acfd = announce("tcp!*!7", adir);
if(acfd < 0)
return −1;
for(;;){
/* listen for a call */
lcfd = listen(adir, ldir);
if(lcfd < 0)
return −1;
/* fork a process to echo */
switch(fork()){
case −1:
perror("forking");
close(lcfd);
break;
case 0:
/* accept the call and open the data file */
dfd = accept(lcfd, ldir);
if(dfd < 0)
return −1;
/* echo until EOF */
while((n = read(dfd, buf, sizeof(buf))) > 0)
write(dfd, buf, n);
exits(0);
default:
close(lcfd);
break;
}
}
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}
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SOURCE
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/usr/local/plan9/src/lib9/dial.c
/usr/local/plan9/src/lib9/announce.c
/usr/local/plan9/src/lib9/_p9dialparse.c
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DIAGNOSTICS
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Dial, announce, and listen return –1 if they fail.
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BUGS
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To avoid name conflicts with the underlying system, dial, announce,
listen, netmkaddr, and reject are preprocessor macros defined
as p9dial, p9announce, and so on; see intro(3).
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