udp_client.h

linux 高级编程的例子源码,包括了本书上的所有代码

#ifndef UDP_CLIENT_H
#define UDP_CLIENT_H
#include "ourhead.h"

int udp_client(const char *host,const char *service,struct sockaddr* sa,socklen_t *salen)
{
	struct hostent *phe;
	struct servent *pse;
	struct sockaddr_in sin;
	int s;
	memset(&sin,0,sizeof(sin));
	sin.sin_family=AF_INET;

	if (pse=getservbyname(service,NULL))
		sin.sin_port=pse->s_port;
	else if ((sin.sin_port=htons((u_short)atoi(service)))==0)
		return -4;

	if (phe=gethostbyname(host))
    {
	     memcpy(&sin.sin_addr,phe->h_addr,phe->h_length);
                memcpy(sa,&sin,sizeof(sin));
                *salen=sizeof(sin);
    }
	else if ((sin.sin_addr.s_addr=inet_addr(host))!=INADDR_NONE)
    {
         memcpy(sa,&sin.sin_addr,sizeof(sin.sin_addr));
                *salen=sizeof(sin);
    }
    else
	       return -3;
        
	s=socket(AF_INET,SOCK_DGRAM,0);
	if (s<0)
		return -2;

	return s;
}
#endif