网络编程

客户端
#include<stdio.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<errno.h>
#include<string.h>
#include<netdb.h>
#include<netinet/in.h>
#include<sys/types.h>
int main(int argc,char *argv[])
{
    int sockfd;
    char buffer[1024];
    struct sockaddr_in server_addr;
    struct hostent * host;
    int portnumber,nbytes;
    if(argc!=3)
    {
        fprintf(stderr,"Usage:%s hostnameportnumber\a\n",argv[0]);
        exit(1);
    }
    if((host=gethostbyname(argv[1]))==NULL)
    {
        fprintf(stderr,"Gethostname error\n");
        exit(1);
    }
    if((portnumber=atof(argv[2]))<0)
    {
        fprintf(stderr,"Usage:%s hostnameportnumber\a\n",argv[0]);
        exit(1);
    }
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
    {
        fprintf(stderr,"Socket ERRor:%s\a\n",strerror(errno));
        exit(1);
    }
    bzero(&server_addr,sizeof(server_addr));
    server_addr.sin_family=AF_INET;
    server_addr.sin_port=htons(portnumber);
    server_addr.sin_addr=*((struct in_addr *)host->h_addr);

    if(connect(sockfd,(struct sockaddr*)(&server_addr),sizeof(struct sockaddr))==-1){
        fprintf(stderr,"Connect Error:%s\a\n",strerror(errno));
        exit(1);
    }
    if((nbytes=read(sockfd,buffer,1024))==-1){
        fprintf(stderr,"Read Error:%s\n",strerror(errno));
        exit(1);
    }
    buffer[nbytes]='\0';
    printf("I have received:%s\n",buffer);
    close(sockfd);
    exit(0);
}

#include<stdlib.h>
#include<stdio.h>
#include<errno.h>
#include<string.h>
#include<netdb.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<sys/socket.h>
int main(int argc ,char * argv[])
{
	int sockfd,new_fd;
	struct sockaddr_in server_addr;
	struct sockaddr_in client_addr;
	int sin_size,portnumber;
	char hello[]="Hello!Are You Fine?\n";
	if(argc!=2){
		fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);
		exit(1);	
	}
	if((portnumber=atoi(argv[1]))<0)
	{
	fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);
	exit(1);
	}
	if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
	{
		fprintf(stderr,"Socket error:%s\n\a",strerror(errno));
		exit(1);
	}
	bzero(&server_addr,sizeof(struct sockaddr_in));
	server_addr.sin_family=AF_INET;
	server_addr.sin_addr.s_addr=htonl(INADDR_ANY);
	server_addr.sin_port=htons(portnumber);
	if(bind(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1){
		fprintf(stderr,"Bind error:%s\n\a",strerror(errno));
		exit(1);
	}	
	if(listen(sockfd,5)==-1){
		fprintf(stderr,"Listen error:%s\n\a",strerror(errno));
		exit(1);
	}	
	while(1)
	{
		sin_size=sizeof(struct sockaddr_in);
		if((new_fd=accept(sockfd,(struct sockaddr *)(&client_addr),&sin_size))==-1){
		fprintf(stderr,"Accept error:%s\n\a",strerror(errno));
		exit(1);		
		}
		fprintf(stderr,"Server get conntction from %s\n",inet_ntoa(client_addr.sin_addr));
		if(write(new_fd,hello,strlen(hello))==-1){
		fprintf(stderr,"Write Error:%s\n",strerror(errno));
		exit(1);
		}
		close(new_fd);
	}	
	close(sockfd);
	exit(0);
}