term% cat index.txt DIAL(2) System Calls Manual DIAL(2)
NAME
dial, hangup, announce, listen, accept, reject, netmkaddr - make and
break network connections
SYNOPSIS
#include <u.h>
#include <libc.h>
int dial(char *addr, char *local, char *dir, int *cfdp)
int hangup(int ctl)
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)
DESCRIPTION
For these routines, addr is a network address of the form network!ne‐
taddr!service, network!netaddr, or simply netaddr. Network is any di‐
rectory listed in /net or the special token, net. Net is a free vari‐
able that stands for any network in common between the source and the
host netaddr. Netaddr can be a host name, a domain name, a network ad‐
dress, or a meta-name of the form $attribute, which is replaced by
value from the value-attribute pair attribute=value most closely asso‐
ciated with the source host in the network data base (see ndb(6)).
If a connection attempt is successful and dir is non-zero, the path
name of a line directory that has files for accessing the connection is
copied into dir. The path name is guaranteed to be less than 40 bytes
long. One line directory exists for each possible connection. The
data file in the line directory should be used to communicate with the
destination. The ctl file in the line directory can be used to send
commands to the line. See dk(3) and ip(3) for messages that can be
written to the ctl file. The last close of the data or ctl file will
close the connection.
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 re‐
turns 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. If the network allows the local address to be set, as
is the case with UDP and TCP port numbers, and local is non-zero, the
local address will be set to local. If cfdp is non-zero, *cfdp is set
to a file descriptor open for reading and writing the control file.
Hangup is a means of forcing a connection to hang up without closing
the ctl and data files.
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 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 re‐
ceived by listen, while reject refuses the call because of cause. Ac‐
cept 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.
EXAMPLES
Make a call and return an open file descriptor to use for communica‐
tions:
int callkremvax(void)
{
return dial("kremvax", 0, 0, 0);
}
Call the local authentication server:
int dialauth(char *service)
{
return dial(netmkaddr("$auth", 0, service), 0, 0, 0);
}
Announce as kremvax on Datakit and loop forever receiving calls and
echoing back to the caller anything sent:
int
bekremvax(void)
{
int dfd, acfd, lcfd;
char adir[40], ldir[40];
int n;
char buf[256];
afd = announce("dk!kremvax", adir);
if(afd < 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;
}
}
}
SOURCE
/sys/src/libc/port
SEE ALSO
auth(2), dk(3), ip(3), stream(3), ndb(8)
DIAGNOSTICS
Dial, announce, and listen return -1 if they fail. Hangup returns non‐
zero if it fails.
DIAL(2)