DIAL(3)

NAME
dial, announce, listen, accept, reject, netmkaddr, getnetconninfo, freenetconninfo, dialparse - make and break network connections

SYNOPSIS
#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,
          void *host, int *port)

DESCRIPTION
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:

      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 `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.

EXAMPLES
Make a call and return an open file descriptor to use for communications:

        int callkremvax(void)
        {
        	return dial("kremvax", 0, 0, 0);
        }

Connect to a Unix socket served by acme(4):

        int dialacme(void)
        {
        	return dial("unix!/tmp/ns.ken.:0/acme", 0, 0, 0);
        }

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(0);
        		default:
        			close(lcfd);
        			break;
        		}
        	}
        }

SOURCE
/usr/local/plan9/src/lib9/dial.c
/usr/local/plan9/src/lib9/announce.c
/usr/local/plan9/src/lib9/_p9dialparse.c
/usr/local/plan9/src/lib9/getnetconn.c

DIAGNOSTICS
Dial, announce, and listen return -1 if they fail.

BUGS
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).