Question

Linux下C语言socket连接验证

Answer 1

客户端
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <errno.h>

#define SERVER_PORT_ID 6081
#define CLIENT_PORT_ID 6086
#define SERVER_HOST_ADDR "128.119.40.186"
/* gaia.cs.umass.edu */
#define MAXSIZE 512

#define ACK 2
#define NACK 3
#define REQUESTFILE 100
#define COMMANDNOTSUPPORTED 150
#define COMMANDSUPPORTED 160
#define BADFILENAME 200
#define FILENAMEOK 400
#define STARTTRANSFER 500
int readn(int sd,char *ptr,int size);
int writen(int sd,char *ptr,int size);

main(int argc,char *argv[])

{

int sockid, newsockid,i,getfile,ack,msg,msg_2,c,len;
int no_writen,start_xfer, num_blks,num_last_blk;
struct sockaddr_in my_addr, server_addr;
FILE *fp;
char in_buf[MAXSIZE];
if(argc != 2)
no_writen = 0;
num_blks = 0;
num_last_blk = 0;
len = strlen(argv[1]);
printf("client: creating socket\n");
if ((sockid = socket(AF_INET,SOCK_STREAM,0)) < 0)
{ printf("client: socket error : %d\n", errno); exit(0);
}

printf("client: binding my local socket\n");
bzero((char *) &my_addr,sizeof(my_addr));
my_addr.sin_family = AF_INET;
my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
my_addr.sin_port = htons(CLIENT_PORT_ID);
if (bind(sockid ,(struct sockaddr *) &my_addr,sizeof(my_addr)) < 0)
{printf("client: bind error :%d\n", errno); exit(0);
}

printf("client: starting connect\n");
bzero((char *) &server_addr,sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = inet_addr(SERVER_HOST_ADDR);
server_addr.sin_port = htons(SERVER_PORT_ID);
if (connect(sockid ,(struct sockaddr *) &server_addr,
sizeof(server_addr)) < 0)
{printf("client: connect error :%d\n", errno); exit(0);
}

/* Once we are here, we've got a connection to the server */
/* tell server that we want to get a file */
getfile = htons(REQUESTFILE);
printf("client: sending command request to ftp server\n");
if((writen(sockid,(char *)&getfile,sizeof(getfile))) < 0)

/* want for go-ahead from server */
msg = 0;
if((readn(sockid,(char *)&msg,sizeof(msg)))< 0)

msg = ntohs(msg);
if (msg==COMMANDNOTSUPPORTED) {
printf("client: server refused command. goodbye\n");
exit(0);
}
else
printf("client: server replied %d, command supported\n",msg);

/* send file name to server */
printf("client: sending filename\n");
if ((writen(sockid,argv[1],len))< 0)

/* see if server replied that file name is OK */
msg_2 = 0;
if ((readn(sockid,(char *)&msg_2,sizeof(msg_2)))< 0)

msg_2 = ntohs(msg_2);
if (msg_2 == BADFILENAME) {
printf("client: server reported bad file name. goodbye.\n");
exit(0);
}
else
printf("client: server replied %d, filename OK\n",msg_2);

/* CLIENT KNOWS SERVER HAS BEEN ABLE TO OPEN THE FILE IN READ
MODE AND IS ASKING FOR GO-AHEAD*/
/* CLIENT NOW OPENS A COPY OF THE FILE IN WRITE MODE AND SENDS
THE GOAHEAD TO SERVER*/
printf("client: sending start transfer command\n");
start_xfer = STARTTRANSFER;
start_xfer = htons(start_xfer);
if ((writen(sockid,(char *)&start_xfer,sizeof(start_xfer)))< 0)
{printf("client: write error :%d\n", errno); exit(0);
}
if ((fp = fopen(argv[1],"w")) == NULL)

/*NOW THE CLIENT IS READING INFORMATION FROM THE SERVER REGARDING HOW MANY
FULL BLOCKS OF SIZE MAXSIZE IT CAN EXPECT. IT ALSO RECEIVES THE NUMBER
OF BYTES REMAINING IN THE LAST PARTIALLY FILLED BLOCK, IF ANY */

if((readn(sockid,(char *)&num_blks,sizeof(num_blks))) < 0)

num_blks = ntohs(num_blks);
printf("client: server responded: %d blocks in file\n",num_blks);
ack = ACK;
ack = htons(ack);
if((writen(sockid,(char *)&ack,sizeof(ack))) < 0)
{printf("client: ack write error :%d\n",errno);exit(0);
}

if((readn(sockid,(char *)&num_last_blk,sizeof(num_last_blk))) < 0)

num_last_blk = ntohs(num_last_blk);
printf("client: server responded: %d bytes last blk\n",num_last_blk);
if((writen(sockid,(char *)&ack,sizeof(ack))) < 0)
{printf("client: ack write error :%d\n",errno);exit(0);
}

/* BEGIN READING BLOCKS BEING SENT BY SERVER */
printf("client: starting to get file contents\n");
for(i= 0; i < num_blks; i ++) {
if((readn(sockid,in_buf,MAXSIZE)) < 0)

no_writen = fwrite(in_buf,sizeof(char),MAXSIZE,fp);
if (no_writen == 0)
if (no_writen != MAXSIZE)

/* send an ACK for this block */
if((writen(sockid,(char *)&ack,sizeof(ack))) < 0)

printf(" %d...",i);
}

/*IF THERE IS A LAST PARTIALLY FILLED BLOCK, READ IT */

if (num_last_blk > 0) {
printf("%d\n",num_blks);
if((readn(sockid,in_buf,num_last_blk)) < 0)

no_writen = fwrite(in_buf,sizeof(char),num_last_blk,fp);
if (no_writen == 0)

if (no_writen != num_last_blk)

if((writen(sockid,(char *)&ack,sizeof(ack))) < 0)

}
else printf("\n");

/*FILE TRANSFER ENDS. CLIENT TERMINATES AFTER CLOSING ALL ITS FILES
AND SOCKETS*/
fclose(fp);
printf("client: FILE TRANSFER COMPLETE\n");
close(sockid);
}

/* DUE TO THE FACT THAT BUFFER LIMITS IN KERNEL FOR THE SOCKET MAY BE
REACHED, IT IS POSSIBLE THAT READ AND WRITE MAY RETURN A POSITIVE VALUE
LESS THAN THE NUMBER REQUESTED. HENCE WE CALL THE TWO PROCEDURES
BELOW TO TAKE CARE OF SUCH EXIGENCIES */

int readn(int sd,char *ptr,int size)

{ int no_left,no_read;
no_left = size;
while (no_left > 0)
{ no_read = read(sd,ptr,no_left);
if(no_read <0) return(no_read);
if (no_read == 0) break;
no_left -= no_read;
ptr += no_read;
}
return(size - no_left);
}

int writen(int sd,char *ptr,int size)
{ int no_left,no_written;
no_left = size;
while (no_left > 0)
{ no_written = write(sd,ptr,no_left);
if(no_written <=0) return(no_written);
no_left -= no_written;
ptr += no_written;
}
return(size - no_left);
}

服务端

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <errno.h>

#define MY_PORT_ID 6081
#define MAXLINE 256
#define MAXSIZE 512

#define ACK 2
#define NACK 3
#define REQUESTFILE 100
#define COMMANDNOTSUPPORTED 150
#define COMMANDSUPPORTED 160
#define BADFILENAME 200
#define FILENAMEOK 400

int writen(int sd,char *ptr,int size);
int readn(int sd,char *ptr,int size);

main() {

int sockid, newsd, pid, clilen;
struct sockaddr_in my_addr, client_addr;

printf("server: creating socket\n");
if ((sockid = socket(AF_INET,SOCK_STREAM,0)) < 0)

printf("server: binding my local socket\n");
bzero((char *) &my_addr,sizeof(my_addr));
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(MY_PORT_ID);
my_addr.sin_addr.s_addr = htons(INADDR_ANY);
if (bind(sockid ,(struct sockaddr *) &my_addr,sizeof(my_addr)) < 0)

printf("server: starting listen \n");
if (listen(sockid,5) < 0)

while(1==1) {
/* ACCEPT A CONNECTION AND THEN CREATE A CHILD TO DO THE WORK */
/* LOOP BACK AND WAIT FOR ANOTHER CONNECTION */
printf("server: starting accept\n");
if ((newsd = accept(sockid ,(struct sockaddr *) &client_addr,
&clilen)) < 0)

printf("server: return from accept, socket for this ftp: %d\n",
newsd);
if ( (pid=fork()) == 0) {
/* CHILD PROC STARTS HERE. IT WILL DO ACTUAL FILE TRANSFER */
close(sockid); /* child shouldn't do an accept */
doftp(newsd);
close (newsd);
exit(0); /* child all done with work */
}
/* PARENT CONTINUES BELOW HERE */
close(newsd); /* parent all done with client, only child */
} /* will communicate with that client from now on */
}