server.c

一个用c语言编写的加密算法。希望大家喜欢

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define PORT 5656
#define BACKLOG 1
#define MAXDATASIZE 100

int dencrypt(char** charb,int size)
{

	int i;
	char *buf;

	buf = (char*)(malloc(size+1));
	buf = charb;

	for(i=0;i<size;i++)
	{

		buf[i] = buf[i]-1;

	}

	charb = buf;
	buf=NULL;
	return 0;
}

int main(void)
{
	int	   listenfd,connectfd;
	struct sockaddr_in  server,client;
	int 	   sin_size;
	int            	   opt;
	char	   buf[MAXDATASIZE];
	int	   numbytes=-1;
	int	   i=0,j;

	if((listenfd=socket(AF_INET,SOCK_STREAM,0))==-1)
	{
		perror("Create socket failed ! ");
		exit(-1);
	}
	
	opt=SO_REUSEADDR;
	setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));
	
	bzero(&server,sizeof(server));
	server.sin_family=AF_INET;
	server.sin_port=htons(PORT);
	server.sin_addr.s_addr=htonl(INADDR_ANY);
	if(bind(listenfd,(struct sockaddr *) (&server) , sizeof(struct sockaddr))==-1)
	{
		perror("Bind error!");
		exit(-1);
	}
	if(listen(listenfd,BACKLOG)==-1)
	{
		perror("Listen error!");
		exit(-1);
	}

	sin_size=sizeof(struct sockaddr_in);

	while(1)
	{
	if((connectfd=accept(listenfd,(struct sockaddr *)&client,&sin_size))==-1)
	{
		perror("Accetp error!");
		exit(-1);
	}
	printf("You get a connection from %s\n",inet_ntoa(client.sin_addr));
	send(connectfd,"Welcome to my server...\nPlease enter the characters. eg:ABC\n  >>",64,0);


		if((numbytes=recv(connectfd,buf,MAXDATASIZE,0))==-1)
		{
			perror("Receive Error !");
			exit(1);
		}
		else
		{
			buf[numbytes]='\0';
			printf("encryptd  characters is >%s  from IP:%s\n",buf,inet_ntoa(client.sin_addr));
			dencrypt(&buf,numbytes);
			send(connectfd,buf,numbytes,0);
			printf("dencryptd characters is >%s\n",buf);
		}
		close(connectfd);
	}

	close(listenfd);
}