Special Thanks to:
Danu Kurniawan n Even
#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 “127.0.0.1″
#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;
int 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){
printf(”error: usage : ftp filename\n”);
exit(0);
}
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);
}
getfile = htons(REQUESTFILE);
printf("sending command request to ftp server\n");
if((writen(sockid,(char *)&getfile,sizeof(getfile))) < 0){
printf("write error:%d\n", errno); exit(0);
}
msg = 0;
if((readn(sockid,(char *)&msg,sizeof(msg)))< 0){
printf("read error:%d\n", errno); exit(0);
}
msg = ntohs(msg);
if(msg==COMMANDNOTSUPPORTED){
printf("server refused command\n"); exit(0);
}
else
printf("server replied %d, command supported\n",msg);
printf("client: sending filename\n");
if((writen(sockid,argv[1],len))< 0){
printf("write error:%d\n", errno);
exit(0);
}
msg_2 = 0;
if((readn(sockid,(char *)&msg_2, sizeof(msg_2)))< 0){
printf("read error:%d\n", errno); exit(0);
}
msg_2 = ntohs(msg_2);
if(msg_2 == BADFILENAME){
printf("server reported bad file name\n");
exit(0);
}
else
printf("server replied filename OK\n");
printf("sending start transfer command\n");
start_xfer = STARTTRANSFER;
start_xfer = htons(start_xfer);
if((writen(sockid,(char *)&start_xfer,sizeof(start_xfer)))< 0){
printf("write error:%d\n", errno);
exit(0);
}
if((fp = fopen(argv[1],"w")) == NULL){
printf("local open file error\n");
exit(0);
}
if((readn(sockid,(char *)&num_blks,sizeof(num_blks))) < 0){
printf("read error on nblocks :%d\n",errno);
exit(0);
}
num_blks = ntohs(num_blks);
printf("server responded: %d blocks in file\n",num_blks);
ack = ACK;
ack = htons(ack);
if((writen(sockid,(char*)&ack,sizeof(ack)))<0){
printf("ack write error :%d\n",errno);
exit(0);
}
if((readn(sockid,(char *)&num_last_blk, sizeof(num_last_blk))) < 0){
printf("read error:%d on nbytes\n",errno);
exit(0);
}
num_last_blk = ntohs(num_last_blk);
printf("server responded: %d bytes last blk\n", num_last_blk);
if((writen(sockid,(char *)&ack,sizeof(ack)))<0){
printf("write error:%d\n",errno);
exit(0);
}
printf("client: starting to get file contents\n");
for(i= 0; i < num_blks; i ++) {
if((readn(sockid,in_buf,MAXSIZE)) < 0){
printf("block error read: %d\n",errno);
exit(0);
}
no_writen=fwrite(in_buf,sizeof(char),MAXSIZE,fp);
if(no_writen == 0){
printf("file write error\n");
exit(0);
}
if (no_writen != MAXSIZE){
printf("write error: no_writen is less\n");
exit(0);
}
if((writen(sockid,(char *)&ack,sizeof(ack))) < 0){
printf("ack write error :%d\n",errno);exit(0);
}
printf(" %d...",i);
}
if(num_last_blk > 0){
printf(”%d\n”,num_blks);
if((readn(sockid,in_buf,num_last_blk)) < 0){
printf("last block error read :%d\n",errno);
exit(0);
}
no_writen=fwrite(in_buf,sizeof(char),num_last_blk,fp);
if(no_writen == 0){
printf("last block file write err :%d\n",errno);
exit(0);
}
if(no_writen != num_last_blk){
printf("file write error : no_writen is less 2\n");
exit(0);
}
if((writen(sockid,(char *)&ack,sizeof(ack))) < 0){
printf("ack write error:%d\n",errno); exit(0);
}
}
else printf("\n");
fclose(fp);
printf("FILE TRANSFER COMPLETE\n");
close(sockid);
}
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);
}
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);
}

