DIAL(2)DIAL(2)
NAME
dial, hangup, announce, listen, accept, reject, netmkaddr, setnetmtpt, getnetconninfo, freenetconninfo – 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)
void setnetmtpt(char *to, int tolen, char *from)
NetConnInfo* getnetconninfo(char *conndir, int fd)
void freenetconninfo(NetConnInfo*)
DESCRIPTION
For these routines,
addr
is a network address of the form
network!netaddr!service,
network!netaddr,
or simply
netaddr.
Network
is any directory listed in
/net
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, a network address,
or a meta-name of the form
$attribute,
which
is replaced by
value
from the value-attribute pair
attribute=value
most closely associated 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
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 all addresses on 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.
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.
unhandled troff command .P
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.
Getnetconninfo
returns a structure containing information about a
network connection. The structure is:
typedef struct NetConnInfo NetConnInfo;
struct NetConnInfo
{
char *dir; /* connection directory */
char *root; /* network root */
char *spec; /* binding spec */
char *lsys; /* local system */
char *lserv; /* local service */
char *rsys; /* remote system */
char *rserv; /* remote service */
char *laddr; /* local address */
char *raddr; /* remote address */
};
The information is obtained from the connection directory,
conndir.
If
conndir
is nil, the directory is obtained by performing
fd2path(2)
on
fd.
Getnetconninfo
returns either a completely specified structure, or
nil if either the structure can’t be allocated or the
network directory can’t be determined.
The structure
is freed using
freenetconninfo.
Setnetmtpt
copies the name of the network mount point into
the buffer
to,
whose length is
tolen.
It exists to merge two pre-existing conventions for specifying
the mount point.
Commands that take a network mount point as a parameter
(such as
dns,
cs
(see
ndb(8)),
and
ipconfig(8))
should now call
setnetmtpt.
If
from
is
nil,
the mount point is set to the default,
/net.
If
from
points to a string starting with a slash,
the mount point is that path.
Otherwise, the mount point is the string pointed to by
from
appended to the string
/net.
The last form is obsolete and is should be avoided.
It exists only to aid in conversion.
EXAMPLES
Make a call and return an open file descriptor to
use for communications:
int callkremvax(void)
{
return dial("kremvax", nil, nil, nil);
}
Call the local authentication server:
int dialauth(char *service)
{
return dial(netmkaddr("$auth", nil, service), nil, nil, nil);
}
Announce as
kremvax
on TCP/IP 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];
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(nil);
default:
close(lcfd);
break;
}
}
}
SOURCE
/sys/src/libc/9sys,
/sys/src/libc/port
SEE ALSO
auth(2),
ip(3),
ndb(8)
DIAGNOSTICS
Dial,
announce,
and
listen
return –1 if they fail.
Hangup
returns nonzero if it fails.