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 net-
work 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 access-
ing the connection is copied into dir. The path name is
guaranteed to be less than 40 bytes long. One line direc-
tory 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
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DIAL(2) DIAL(2)
or ctl file will close the connection.
Dial makes a call to destination addr on a multiplexed net-
work. If the network in addr is net, dial will try all
addresses on networks in common between source and destina-
tion 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.
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 indi-
cate all local addresses, e.g. tcp!*!echo. The listen rou-
tine 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 announc-
ing. 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 */
};
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DIAL(2) DIAL(2)
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 struc-
ture 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);
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DIAL(2) DIAL(2)
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.
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