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TCP/IP program to allocate and connect a socket using TCP or UDP

Posted By: Milind Mishra     Category: Networking     Views: 3294

TCP/IP program to allocate and connect a socket using TCP or UDP.

Code for TCP/IP program to allocate and connect a socket using TCP or UDP in Networking

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

#include <netinet/in.h>
#include <arpa/inet.h>

#include <netdb.h>
#include <string.h>
#include <stdlib.h>

#ifndef    INADDR_NONE
#define    INADDR_NONE    0xffffffff
#endif/* INADDR_NONE */externint    errno;

int    errexit(constchar *format, ...);

int
connectsock(constchar *host, constchar *service, constchar *transport )
/* * Arguments: *      host      - name of host to which connection is desired *      service   - service associated with the desired port *      transport - name of transport protocol to use ("tcp" or "udp") */
{
    struct hostent    *phe;    /* pointer to host information entry    */struct servent    *pse;    /* pointer to service information entry    */struct protoent *ppe;    /* pointer to protocol information entry*/struct sockaddr_in sin;    /* an Internet endpoint address        */int    s, type;    /* socket descriptor and socket type    */


    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;

    /* Map service name to port number */if ( pse = getservbyname(service, transport) )
        sin.sin_port = pse->s_port;
    elseif ( (sin.sin_port = htons((u_short)atoi(service))) == 0 )
        errexit("can't get \"%s\" service entry\n", service);

    /* Map host name to IP address, allowing for dotted decimal */if ( phe = gethostbyname(host) )
        memcpy(&sin.sin_addr, phe->h_addr, phe->h_length);
    elseif ( (sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE )
        errexit("can't get \"%s\" host entry\n", host);

    /* Map transport protocol name to protocol number */if ( (ppe = getprotobyname(transport)) == 0)
        errexit("can't get \"%s\" protocol entry\n", transport);

    /* Use protocol to choose a socket type */if (strcmp(transport, "udp") == 0)
        type = SOCK_DGRAM;
    else
        type = SOCK_STREAM;

    /* Allocate a socket */
    s = socket(PF_INET, type, ppe->p_proto);
    if (s < 0)
        errexit("can't create socket: %s\n", strerror(errno));

    /* Connect the socket */if (connect(s, (struct sockaddr *)&sin, sizeof(sin)) < 0)
        errexit("can't connect to %s.%s: %s\n", host, service,
            strerror(errno));
    return s;
}
  
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Milind Mishra
Milind Mishra author of TCP/IP program to allocate and connect a socket using TCP or UDP is from India.
 
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