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This section explains the calls your server process must make to
connect with and serve a client process. Creating a Socket | |
The server
process must call socket to create
a communication endpoint. 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; |
- Function result:
socket number (HP-UX file descriptor), -1
if failure occurs.
Example: s = socket (AF_INET, SOCK_STREAM, 0); |
The socket number returned is the socket descriptor for the newly created socket.
This number is an HP-UX file descriptor and can be used for reading,
writing or any standard file system calls after a BSD Sockets
connection is established. A socket descriptor is treated like a
file descriptor for an open file. The server process should create a socket before any other
BSD Sockets system calls. Refer to the socket(2)
man page for more information on socket. Binding a Socket Address to the Server Process's Socket | |
After your server process has created
a socket, it must call bind to
bind a socket address. Until an address is bound to the server socket,
other processes have no way to reference it. The server process must bind a specific port address
to this socket, which is used for listening. Otherwise, a client
process would not know what port to connect to for the desired service. Set up the address structure with a local address before you
make a bind call. Use a wildcard
address so your server process does not have to look up its own
internet address. bind and its
parameters are described in the following table. - Include files:
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h> |
- System call:
bind (s, addr, addrlen)
int s;
struct sockaddr *addr;
int addrlen; |
- Function result:
0 if bind is successful, -1 if failure
occurs.
Example: struct sockaddr_in myaddr;
...
bind (ls, &myaddr, sizeof(struct sockaddr_in)); |
When to Bind Socket Addresses The server process should bind the socket address after the
socket is created and before any other BSD Sockets system calls.
Refer to the bind(2) man page for
more information on bind. Setting Up the Server to Wait for Connection Requests | |
Once your server process has an address bound to it, it must
call listen to set up a queue that
accepts incoming connection requests. The
server process then monitors the queue for requests (using select(2)
or accept ). The server process cannot
respond to a connection request until it has executed listen. listen
and its parameters are described
in the following table. - Include files:
none - System call:
listen(s, backlog)
int s, backlog; |
- Function result:
0 if listen is successful, -1 if failure
occurs.
Example: backlog is the preferred
number of unaccepted incoming connections allowed at a given time.
The actual number may be greater than the specified backlog. When
the request is full, further connection requests are rejected. A backlog of 0 specifies only 1 pending connection can exist
at any given time. SOMAXCONN is defined in <sys/socket.h>.
The default setting is 20. When to Set Up Server to Listen The server process should be set up to listen after socket
is created and bound and before the server can respond to connection
requests. Refer to the listen(2)
man page for more information on listen. Accepting a Connection | |
The server process can accept any connection requests that enter its queue
after it executes listen. accept
creates a new socket for the connection and returns the socket descriptor
for the new socket. The new socket: Is created with the
same properties as the old socket. Has the same bound port address as the old socket. Is connected to the client process's socket.
accept blocks until there
is a connection request from a client process in the queue, unless
you are using nonblocking I/O. accept
and its parameters are described in the following table. - Include files:
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h> |
- System call:
s = accept(ls,addr,addrlen)
int s;
int ls;
struct sockaddr *addr;
int *addrlen; |
- Function result:
socket descriptor of new socket if accept is successful,
-1 if failure occurs.
Example: struct sockaddr_in peeraddr;
...
addrlen = sizeof(sockaddr_in);
s = accept (ls, &peeraddr, &addrlen); |
There is no way for the server process to indicate which requests
it can accept. It must accept all requests or none. Your server
process can keep track of which process a connection request is
from by examining the address returned by accept.
Once you have this address, you can use gethostbyaddr
to get the hostname. You can close down the connection if you do
not want the server process to communicate with that particular
client host or port. When to Accept a Connection The server process should accept a connection after executing
the listen call. Refer to the accept(2)
man page for more information on accept. |
