Writing the Server and Client Processes

This section discusses the calls your server and client processes must make.

Creating Sockets

Both processes must call socket to create communication endpoints. socket and its parameters are described in the following table.

Include files:

#include <sys/types.h> 
#include <sys/socket.h>

System call:

s = socket(af, type, protocol) 
int af, type, protocol;

Parameter	Description of Contents	INPUT Value
af	address family	AF_UNIX
type	socket type	SOCK_DGRAM
protocol	underlying protocol to be used	0 (default)

Function result:

socket number (HP-UX file descriptor) if successful, -1 if socket call fails.

Example:

#include <sys/type.h>
#include <sys/socket.h>
...
s = socket(AF_UNIX, SOCK_DGRAM, 0)

When to Create Sockets

The server or client process should create sockets before any other BSD Sockets system calls. Refer to the socket(2) man page for more information on socket.

Binding Socket Addresses to UNIX Domain Datagram Sockets

After your server process has created a socket, it must call bind to bind a socket address. Until the server socket is bound to an address, other processes have no way to reference it.

The server process must bind a specific pathname to its socket. Set up the address structure with a local address before the server makes a call to bind.

The bind system call creates the inode file. If the inode file is not deallocated after bound sockets are closed, the names will continue to exist and cause directories to fill up with the unused files. To avoid directories filling up with these unused files, you can remove the files by calling unlink or remove them manually with the rm command. bind and its parameters are described in the following table.

Include files:

#include <sys/types.h> 
#include <sys/socket.h> 
#include <sys/un.h>

System call:

bind(s, addr, addrlen); 
int s; 
struct sockaddr_un *addr; 
int addrlen;

Parameter	Description of Contents	INPUT Value
s	socket descriptor of local socket	socket descriptor of socket to be bound
addr	socket address	pointer to address to be bound to s
addrlen	length of socket address	size of struct sockaddr_un address

Function result:

0 if bind is successful, -1 if bind fails.

Example:

#include <sys/type.h>
#include <sys/socket.h>
#include <sys/un.h>
#define  SOCKET_PATH "/tmp/myserver"
struct  sockaddr_un     servaddr;
...
servaddr.sun_family = AF_UNIX;
strcpy(servaddr.sun_path, SOCKET_PATH);
unlink(SOCKET_PATH);
bind(s, &servaddr, sizeof(struct sockaddr_un));

When to Bind Socket Addresses

The server process should bind socket addresses after socket is created and before any other BSD Sockets system calls. Refer to the bind(2) man page for more information on bind.

Writing the Server and Client Processes

Technical documentation

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Creating Sockets

When to Create Sockets

Binding Socket Addresses to UNIX Domain Datagram Sockets

When to Bind Socket Addresses