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NAME
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dial, announce, listen, accept, reject, netmkaddr, getnetconninfo,
freenetconninfo, 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)
NetConnInfo* getnetconninfo(char *dir, int fd)
void freenetconninfo(NetConnINfo*)
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 call. 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. Dial’s 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.
Netmkaddr also translates Unix conventions into Plan 9 syntax.
If addr is the name of a local file or Unix domain socket, netmkaddr
will return unix!addr. If addr is of the form host:port, netmkaddr
will return net!host!port.
Dialparse parses a network address as described above into a network
name, a Unix domain socket address, an IP host address, and an
IP port number.
Getnetconninfo returns a structure containing information about
a network connection. The structure is:
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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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The information is obtained from the ‘line directory’ dir, or
if dir is nil, from the connection file descriptor 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.
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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
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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