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The following program was broken into steps to show how a connection
is established between two sockets. Establish the connection in loopback, using a single process:
#include </stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/in.h>
#include <sys/errno.h>
#include <fcntl.h>
#include <unistd.h>
main()
{
int sock;
int peer1;
int struc_len;
int fret;
int sock2;
struct sockaddr_in sockaddr;
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Create the two sockets:
sock=socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sock == -1)
print ("Error creating socket.\n");
peer1 = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (peer1 == -1)
printf ("Error creating socket.\n");
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Create
the socket structure to bind the socket. The IP address used is 0
(loopback), and the SAP is set to an arbitrary constant (4444). This
structure is used for both the bind and the connect:
sockaddr.sin_family = AF_INET;
sockaddr.sin_addr.s_addr = INADDR_THISHOST;
sockaddr.sin_port = 4444;
struc_len = 16;
if (bind (sock, (struct sockaddr *)&sockaddr,
sizeof (sockaddr)) < 0 )
printf ("Bind failed\n);
listen (sock,10);
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Set
the socket initiating the connection to be nonblocking. This allows
the connect to return to the user without blocking and
waiting for accept:
| | | |  | NOTE: The sfcntl function should be used until the
fcntl is provided by the operating system.
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sfcntl (peer1, F_SETFL, O_NONBLOCK);
fret = connect (peer1, (struct sockaddr *) &sockaddr, struc_len);
if (fret == -1)
printf ("Connect failed with error %d\n",errno);
else
printf ("Connect succeeded\n");
sock2 = accept (sock, (struct sockaddr *) &sockaddr, &struc_len);
if (sock2 == -1)
printf ("Accept failed\n");
else
printf ("Accept succeeded\n");
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Call recv to complete the connection:
recv (peer1, 0,0,0);
} /* end main */ |
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