Network Programming Lab, Study notes of Network Programming

Download Network Programming Lab and more Study notes Network Programming in PDF only on Docsity! Department of Information Technology Faculty of Engineering And Technology Lab Manual SUBJECT CODE / TITLE: IT0421/ NETWORKING LAB Prepared By Mr. S.Muruganandam & Mr. A.R.Nagoor Meeran Assistant professor(O.G), Assistant Professor(O.G), Department of Information Technology SRM University, SRM Nagar, Kattankulathur-603203 Kancheepuram District, Tamilnadu Page | 1 IT 0421 NETWORKING LAB 0 0 3 2 Co requisite IT 0405 TCP/IP Technology PURPOSE The purpose of this course is to implement various protocols used in networking and analyze them. INSTRUCTIONAL OBJECTIVES After successful completion of the course, the students should be able to • To implement File transfer protocols • To learn and implement RPCs • To implement DES and RSA encryption/decryption schemes • To implement packet capturing and analysis • To implement Chatting mechanism • To configure and implement firewalls. • To design and implant simple IDS LIST OF EXPERIMENTS 1. Study of Header Files 2. Study of Basic Functions of Socket Programming 3. Simple Tcp/Ip Client Server Communication 4. Udp Echo Client Server Communication 5. Concurrent Tcp/Ip Day-Time Server 6. Half Duplex Chat Using Tcp/Ip 7. Full Duplex Chat Using Tcp/Ip 8. Implementation Of File Transfer Protocol 9. Remote Command Execution Using Udp 10. Arp Implementation Using Udp TOTAL 60 Page | 2 11. sys/ioctl.h: Macros and defines used in specifying an ioctl request are located in this header file. We use the function ioctl() that is defined in this header file. ioctl() function is used to perform ARP cache operations. 12. pcap.h: Has function definitions that are required for packet capturing. Some of the functions are pcap_lookupdev(),pcap_open_live() and pcap_loop(). pcap_lookupdev() is used to initialize the network device.The device to be sniffed is opened using the pcap_open_live(). Pcap_loop() determines the number of packets to be sniffed. 13. net/if_arp.h: Contains the definitions for Address Resolution Protocol. We use this to manipulate the ARP request structure and its data members arp_pa,arp_dev and arp_ha. The arp_ha structure’s data member sa_data[ ] has the hardware address. 14. errno.h: It sets an error number when an error and that error can be displayed using perror function. It has symbolic error names. The error number is never set to zero by any library function. 15. arpa/inet.h: This is used to convert internet addresses between ASCII strings and network byte ordered binary values (values that are stored in socket address structures). It is used for inet_aton, inet_addr, inet_ntoa functions. Page | 5 Ex No: 2 Date: STUDY OF BASIC FUNCTIONS OF SOCKET PROGRAMMING AIM: To discuss some of the basic functions used for socket programming. 1.man socket NAME: Socket – create an endpoint for communication. SYNOPSIS: #include<sys/types.h> #include<sys/socket.h> int socket(int domain,int type,int protocol); DESCRIPTION: Socket creates an endpoint for communication and returns a descriptor. The domain parameter specifies a common domain this selects the protocol family which will be used for communication. These families are defined in <sys/socket.h>. FORMAT: NAME PURPOSE PF_UNIX,PF_LOCAL Local Communication. PF_INET IPV4 Internet Protocols. PF_IPX IPX-Novell Protocols. PF_APPLETALK Apple Talk. The socket has the indicated type, which specifies the communication semantics. TYPES: 1.SOCK_STREAM: Provides sequenced , reliable, two-way , connection based byte streams. Page | 6 An out-of-band data transmission mechanism, may be supported. 2.SOCK_DGRAM: Supports datagram (connectionless, unreliable messages of a fixed maximum length). 3.SOCK_SEQPACKET: Provides a sequenced , reliable, two-way connection based data transmission path for datagrams of fixed maximum length. 4.SOCK_RAW: Provides raw network protocol access. 5.SOCK_RDM: Provides a reliable datagram layer that doesn’t guarantee ordering. 6.SOCK_PACKET: Obsolete and shouldn’t be used in new programs. 2.man connect: NAME: connect – initiate a connection on a socket. SYNOPSIS: #include<sys/types.h> #include<sys/socket.h> int connect(int sockfd,const (struct sockaddr*)serv_addr,socklen_t addrlen); DESCRIPTION: The file descriptor sockfd must refer to a socket. If the socket is of type SOCK_DGRAM then the serv_addr address is the address to which datagrams are sent by default and the only addr from which datagrams are received. If the socket is of type SOCK_STREAM or SOCK_SEQPACKET , this call attempts to make a connection to another socket. RETURN VALUE: If the connection or binding succeeds, zero is returned. On error , -1 is returned , and error number is set appropriately. ERRORS: EBADF Not a valid Index. EFAULT The socket structure address is outside the user’s address space. ENOTSOCK Not associated with a socket. EISCONN Socket is already connected. ECONNREFUSED No one listening on the remote address. 3.man accept Page | 7 ifconfig interface[aftype] options | address…… DESCRIPTION: ifconfig is used to configure the kernel resident network interfaces. It is used at boot time to setup interfaces as necessary. After that, it is usually only needed when debugging or when system tuning is needed. If no arguments are given, ifconfig displays the status of the currently active interfaces. 9. man bind SYNOPSIS: bind[-m keymap] [-lp sv psv] 10. man htons/ man htonl NAME: htonl, htons, ntohl, ntohs - convert values between host and network byte order. SYNOPSIS: #include<netinet/in.h> uint32_t htonl(uint32_t hostlong); uint16_t htons(uint32_t hostshort); uint32_t ntohl(uint32_t netlong); uint16_t ntohs(uint16_t netshort); DESCRIPTION: The htonl() function converts the unsigned integer hostlong from host byte order to network byte order. The htons() converts the unsigned short integer hostshort from host byte order to network byte order. The ntohl() converts the unsigned integer netlong from network byte order to host byte order. 11. man gethostname NAME: gethostname, sethostname- get/set host name. SYNOPSIS: #include<unistd.h> int gethostname(char *name,size_t len); int sethostname(const char *name,size_t len); DESCRIPTION: Page | 10 These functions are used to access or to change the host name of the current processor. The gethostname() returns a NULL terminated hostname(set earlier by sethostname()) in the array name that has a length of len bytes. In case the NULL terminated then hostname does not fit ,no error is returned, but the hostname is truncated. It is unspecified whether the truncated hostname will be NULL terminated. 12. man gethostbyname NAME: gethostbyname, gethostbyaddr, sethostent, endhostent, herror, hstr – error – get network host entry. SYNOPSIS: #include<netdb.h> extern int h_errno; struct hostent *gethostbyname(const char *name); #include<sys/socket.h> struct hostent *gethostbyaddr(const char *addr)int len, int type); struct hostent *gethostbyname2(const char *name,int af); DESCRIPTION: The gethostbyname() returns a structure of type hostent for the given hostname. Name->hostname or IPV4/IPV6 with dot notation. gethostbyaddr()- struct of type hostent / host address length Address types- AF_INET, AF_INET6. sethostent() – stay open is true(1). TCP socket connection should be open during queries. Server queries for UDP datagrams. endhostent()- ends the use of TCP connection. Members of hostent structure: a) h_name b) h_aliases c) h_addrtype d) h_length e) h_addr-list f) h_addr. RESULT: Thus the basic functions used for Socket Programming was studied successfully. Page | 11 Ex No: 3 Date: SIMPLE TCP/IP CLIENT SERVER COMMUNICATION GIVEN REQUIREMENTS: There are two hosts, Client and Server. The Client accepts the message from the user and sends it to the Server. The Server receives the message and prints it. TECHNICAL OBJECTIVE: To implement a simple TCP Client-Server application , where the Client on establishing a connection with the Server, sends a string to the Server. The Server reads the String and prints it. METHODOLOGY: Server: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to a dynamically assigned port number. Bind the local host address to socket using the bind function. Listen on the socket for connection request from the client. Accept connection request from the client using accept function. Within an infinite loop, using the recv function receive message from the client and print it on the console. Client: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET. Get the server IP address and port number from the console. Using gethostbyname function assign it to a hostent structure, and assign it to sin_addr of the server address structure. Request a connection from the server using the connect function. Within an infinite loop, read message from the console and send the message to the server using the send function. CODING: Server: tcpserver.c #include<sys/types.h> #include<sys/socket.h> #include<netinet/in.h> #include<netdb.h> #include<arpa/inet.h> #include<string.h> Page | 12 hi Data Sent hi Enter the message: how r u Data Sent how r u Enter the message: INFERENCE: Thus, a program to perform simple communication between client and server using TCP/IP was implemented. Page | 15 Ex No: 4 Date: UDP ECHO CLIENT SERVER COMMUNICATION GIVEN REQUIREMENTS: There are two hosts, Client and Server. The Client accepts the message from the user and sends it to the Server. The Server receives the message, prints it and echoes the message back to the Client. TECHNICAL OBJECTIVE: To implement an UDP Echo Client-Server application , where the Client on establishing a connection with the Server, sends a string to the Server. The Server reads the String, prints it and echoes it back to the Client. METHODOLOGY: Server: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_DGRAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to SERVER_PORT, a macro defined port number. Bind the local host address to socket using the bind function. Within an infinite loop, receive message from the client using recvfrom function, print it on the console and send (echo) the message back to the client using sendto function. Client: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_DGRAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET. Get the server IP address from the console. Using gethostbyname function assign it to a hostent structure, and assign it to sin_addr of the server address structure. Within an infinite loop, read message from the console and send the message to the server using the sendto function. Receive the echo message using the recvfrom function and print it on the console. CODING: Server: udpserver.c #include<sys/socket.h> #include<stdio.h> #include<unistd.h> #include<string.h> #include<netinet/in.h> #include<netdb.h> Page | 16 #include<arpa/inet.h> #include<sys/types.h> int main(int argc,char *argv[]) { int sd; char buff[1024]; struct sockaddr_in cliaddr,servaddr; socklen_t clilen; clilen=sizeof(cliaddr); /*UDP socket is created, an Internet socket address structure is filled with wildcard address & server’s well known port*/ sd=socket(AF_INET,SOCK_DGRAM,0); if (sd<0) { perror ("Cannot open Socket"); exit(1); } bzero(&servaddr,sizeof(servaddr)); /*Socket address structure*/ servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(5669); /*Bind function assigns a local protocol address to the socket*/ if(bind(sd,(struct sockaddr*)&servaddr,sizeof(servaddr))<0) { perror("error in binding the port"); exit(1); } printf("%s","Server is Running…\n"); while(1) { bzero(&buff,sizeof(buff)); /*Read the message from the client*/ if(recvfrom(sd,buff,sizeof(buff),0,(struct sockaddr*)&cliaddr,&clilen)<0) { perror("Cannot rec data"); exit(1); } printf("Message is received \n",buff); /*Sendto function is used to echo the message from server to client side*/ if(sendto(sd,buff,sizeof(buff),0,(struct sockadddr*)&cliaddr,clilen)<0) { Page | 17 Enter input data : how are u Data sent to UDP Server:how are u Received Data from server: how are u Enter input data : INFERENCE: Thus, the UDP ECHO client server communication is established by sending the message from the client to the server and server prints it and echoes the message back to the client. Page | 20 Ex No:5 Date: CONCURRENT TCP/IP DAY-TIME SERVER GIVEN REQUIREMENTS: There are two hosts, Client and Server. The Client requests the concurrent server for the date and time. The Server sends the date and time, which the Client accepts and prints. TECHNICAL OBJECTIVE: To implement a TCP/IP day time server (concurrent server) that handles multiple client requests. Once the client establishes connection with the server, the server sends its day-time details to the client which the client prints in its console. METHODOLOGY: Server: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to statically assigned port number. Bind the local host address to socket using the bind function. Within a for loop, accept connection request from the client using accept function. Use the fork system call to spawn the processes. Calculate the current date and time using the ctime() function. Change the format so that it is appropriate for human readable form and send the date and time to the client using the write function. Client: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET. Get the server IP address from the console. Using gethostbyname function assign it to a hostent structure, and assign it to sin_addr of the server address structure. Request a connection from the server using the connect function. Within an infinite loop, receive the date and time from the server using the read function and print the date and time on the console. CODING: Server: dtserver.c #include<time.h> #include<sys/types.h> #include<sys/socket.h> #include<unistd.h> #include<stdio.h> Page | 21 #include<string.h> #include<netinet/in.h> #include<netdb.h> 0int main(int argc,char *argv[]) { int sd,ad; char buff[1024]; struct sockaddr_in servaddr,cliaddr; //socklen_t clilen=sizeof(cliaddr); time_t t1; bzero(&servaddr,sizeof(servaddr)); /*Socket address structure*/ servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(1507); /*TCP socket is created, an Internet socket address structure is filled with wildcard address & server’s well known port*/ sd=socket(AF_INET,SOCK_STREAM,0); /*Bind function assigns a local protocol address to the socket*/ bind(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); /*Listen function specifies the maximum number of connections that kernel should queue for this socket*/ listen(sd,5); printf("Server is running…\n"); /*The server to return the next completed connection from the front of the completed connection Queue calls it*/ ad=accept(sd,(struct sockaddr *)NULL,NULL); while(1) { bzero(&buff,sizeof(buff)); /*Library function time returns the Coordinated Universal Time*/ t1=time(NULL); /*Prints the converted string format*/ snprintf(buff,sizeof(buff),"%24s\r\n",ctime(&t1)); send(ad,buff,sizeof(buff),0); } Client: dtclient.c #include<stdio.h> Page | 22 Ex No:6 Date: HALF DUPLEX CHAT USING TCP/IP GIVEN REQUIREMENTS: There are two hosts, Client and Server. Both the Client and the Server exchange message i.e. they send messages or receive message from the other. There is only a single way communication between them. TECHNICAL OBJECTIVE: To implement a half duplex application, where the Client establishes a connection with the Server. The Client can send and the server well receive messages at the same time. METHODOLOGY: Server: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to dynamically assigned port number. Bind the local host address to socket using the bind function. Listen on the socket for connection request from the client. Accept connection request from the Client using accept function. Fork the process to receive message from the client and print it on the console. Read message from the console and send it to the client. Client: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET. Get the server IP address and the Port number from the console. Using gethostbyname function assign it to a hostent structure, and assign it to sin_addr of the server address structure. Request a connection from the server using the connect function. Fork the process to receive message from the server and print it on the console. Read message from the console and send it to the server. CODING: Server: hserver.c #include<sys/types.h> #include<stdio.h> #include<netdb.h> #include<sys/socket.h> #include<arpa/inet.h> #include<unistd.h> #include<netinet/in.h> Page | 25 int main(int argc,char *argv[]) { int n,sd,ad; struct sockaddr_in servaddr,cliaddr; socklen_t clilen,servlen; char buff[10000],buff1[10000]; bzero(&servaddr,sizeof(servaddr)); /*Socket address structure*/ servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(5000); /*TCP socket is created, an Internet socket address structure is filled with wildcard address & server’s well known port*/ sd=socket(AF_INET,SOCK_STREAM,0); /*Bind function assigns a local protocol address to the socket*/ bind(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); /*Listen function specifies the maximum number of connections that kernel should queue for this socket*/ listen(sd,5); printf("%s\n","server is running…"); /*The server to return the next completed connection from the front of the completed connection Queue calls it*/ ad=accept(sd,(struct sockaddr*)&cliaddr,&clilen); while(1) { bzero(&buff,sizeof(buff)); /*Receiving the request from client*/ recv(ad,buff,sizeof(buff),0); printf("Receive from the client:%s\n",buff); n=1; while(n==1) { bzero(&buff1,sizeof(buff1)); printf("%s\n","Enter the input data:"); /*Read the message from client*/ fgets(buff1,10000,stdin); /*Sends the message to client*/ send(ad,buff1,strlen(buff1)+1,0); printf("%s\n","Data sent"); n=n+1; } } Page | 26 return 0; } Client: hclient.c #include<sys/types.h> #include<sys/socket.h> #include<arpa/inet.h> #include<netinet/in.h> #include<unistd.h> #include<stdio.h> #include<netdb.h> int main(int argc,char *argv[]) { int n,sd,cd; struct sockaddr_in servaddr,cliaddr; socklen_t servlen,clilen; char buff[10000],buff1[10000]; bzero(&servaddr,sizeof(servaddr)); /*Socket address structure*/ servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=inet_addr(argv[1]); servaddr.sin_port=htons(5000); /*Creating a socket, assigning IP address and port number for that socket*/ sd=socket(AF_INET,SOCK_STREAM,0); /*Connect establishes connection with the server using server IP address*/ cd=connect(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); while(1) { bzero(&buff,sizeof(buff)); printf("%s\n","Enter the input data:"); /*This function is used to read from server*/ fgets(buff,10000,stdin); /*Send the message to server*/ send(sd,buff,strlen(buff)+1,0); printf("%s\n","Data sent"); n=1; while(n==1) { bzero(&buff1,sizeof(buff1)); Page | 27 Ex No:7 Date: FULL DUPLEX CHAT USING TCP/IP GIVEN REQUIREMENTS: There are two hosts, Client and Server. Both the Client and the Server exchange message i.e. they send messages to and receive message from the other. There is a two way communication between them. TECHNICAL OBJECTIVE: To implement a full duplex application, where the Client establishes a connection with the Server. The Client and Server can send as well as receive messages at the same time. Both the Client and Server exchange messages. METHODOLOGY: Server: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to dynamically assigned port number. Bind the local host address to socket using the bind function. Listen on the socket for connection request from the client. Accept connection request from the Client using accept function. Fork the process to receive message from the client and print it on the console. Read message from the console and send it to the client. Client: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET. Get the server IP address and the Port number from the console. Using gethostbyname function assign it to a hostent structure, and assign it to sin_addr of the server address structure. Request a connection from the server using the connect function. Fork the process to receive message from the server and print it on the console. Read message from the console and send it to the server. CODING: Server: fserver.c #include<sys/types.h> #include<sys/socket.h> #include<stdio.h> #include<unistd.h> #include<netdb.h> #include<arpa/inet.h> Page | 30 #include<netinet/in.h> int main(int argc,char *argv[]) { int ad,sd; struct sockaddr_in servaddr,cliaddr; socklen_t servlen,clilen; char buff[1000],buff1[1000]; pid_t cpid; bzero(&servaddr,sizeof(servaddr)); /*Socket address structure*/ servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(5500); /*TCP socket is created, an Internet socket address structure is filled with wildcard address & server’s well known port*/ sd=socket(AF_INET,SOCK_STREAM,0); /*Bind function assigns a local protocol address to the socket*/ bind(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); /*Listen function specifies the maximum number of connections that kernel should queue for this socket*/ listen(sd,5); printf("%s\n","Server is running......."); /*The server to return the next completed connection from the front of the completed connection Queue calls it*/ ad=accept(sd,(struct sockaddr*)&cliaddr,&clilen); /*Fork system call is used to create a new process*/ cpid=fork(); if(cpid==0) { while(1) { bzero(&buff,sizeof(buff)); /*Receiving the request from client*/ recv(ad,buff,sizeof(buff),0); printf("Received message from the client:%s\n",buff); } } else { while(1) { Page | 31 bzero(&buff1,sizeof(buff1)); printf("%s\n","Enter the input data:"); /*Read the message from client*/ fgets(buff1,10000,stdin); /*Sends the message to client*/ send(ad,buff1,strlen(buff1)+1,0); printf("%s\n","Data sent…"); } } return 0; } Client: fclient.c #include<sys/socket.h> #include<sys/types.h> #include<stdio.h> #include<arpa/inet.h> #include<unistd.h> #include<netdb.h> #include<netinet/in.h> int main(int argc,char *argv[]) { int sd,cd; struct sockaddr_in servaddr,cliaddr; socklen_t servlen,clilen; char buff[1000],buff1[1000]; pid_t cpid; bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=inet_addr(argv[1]); servaddr.sin_port=htons(5500); /*Creating a socket, assigning IP address and port number for that socket*/ sd=socket(AF_INET,SOCK_STREAM,0); /*Connect establishes connection with the server using server IP address*/ cd=connect(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); /*Fork is used to create a new process*/ cpid=fork(); if(cpid==0) { while(1) { bzero(&buff,sizeof(buff)); Page | 32 Ex No: 8 Date: IMPLEMENTATION OF FILE TRANSFER PROTOCOL GIVEN REQUIREMENTS: There are two hosts, Client and Server. The Client sends the name of the file it needs from the Server and the Server sends the contents of the file to the Client, where it is stored in a file. TECHNICAL OBJECTIVE: To implement FTP application, where the Client on establishing a connection with the Server sends the name of the file it wishes to access remotely. The Server then sends the contents of the file to the Client, where it is stored. METHODOLOGY: Server: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to dynamically assigned port number. Bind the local host address to socket using the bind function. Listen on the socket for connection request from the client. Accept connection request from the Client using accept function. Within an infinite loop, receive the file name from the Client. Open the file, read the file contents to a buffer and send the buffer to the Client. Client: Include the necessary header files. Create a socket using socket function with family AF_INET, type as SOCK_STREAM. Initialize server address to 0 using the bzero function. Assign the sin_family to AF_INET. Get the server IP address and the Port number from the console. Using gethostbyname function assign it to a hostent structure, and assign it to sin_addr of the server address structure. Within an infinite loop, send the name of the file to be viewed to the Server. Receive the file contents, store it in a file and print it on the console. CODING: Server: ftps.c #include<sys/types.h> #include<sys/socket.h> #include<sys/stat.h> #include<arpa/inet.h> #include<netinet/in.h> #include<netdb.h> #include<unistd.h> #include<stdio.h> Page | 35 #include<string.h> int main(int argc,char *argv[]) { int sd,ad,size; struct sockaddr_in servaddr,cliaddr; socklen_t clilen; clilen=sizeof(cliaddr); struct stat x; char buff[100],file[10000]; FILE *fp; bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(1500); sd=socket(AF_INET,SOCK_STREAM,0); bind(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); listen(sd,5); printf("%s\n","Server Is Running...."); ad=accept(sd,(struct sockaddr*)&cliaddr,&clilen); while(1) { bzero(buff,sizeof(buff)); bzero(file,sizeof(file)); recv(ad,buff,sizeof(buff),0); fp=fopen(buff,"r"); stat(buff,&x); size=x.st_size; fread(file,sizeof(file),1,fp); send(ad,file,sizeof(file),0); } } Client: ftpc.c #include<sys/types.h> #include<sys/socket.h> #include<netinet/in.h> #include<arpa/inet.h> #include<netdb.h> #include<stdio.h> #include<unistd.h> int main(int argc,char *argv[]) { int sd,cd; struct sockaddr_in servaddr,cliaddr; socklen_t clilen; char buff[100],file[10000]; struct hostent *h; Page | 36 h=gethostbyname(argv[1]); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=h->h_addrtype; memcpy((char *)&servaddr.sin_addr.s_addr,h->h_addr_list[0],h->h_length); servaddr.sin_port=htons(1500); sd=socket(AF_INET,SOCK_STREAM,0); cd=connect(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); while(1) { printf("%s\n","Enter the File Name :"); scanf("%s",buff); send(sd,buff,strlen(buff)+1,0); printf("%s\n","File Output :"); recv(sd,file,sizeof(file),0); printf("%s",file); } return 0; } SAMPLE OUTPUT: Server: (Host Name:Root1) [root@localhost 4ita33]# vi ftps.c [root@localhost 4ita33]# cc ftps.c [root@localhost 4ita33]# ./a.out Server is Running… FILE REACHED File output : this is my network lab Client: (Host Name:Root2) [root@localhost 4ita33]# vi ftpc.c [root@localhost 4ita33]# cc ftpc.c [root@localhost 4ita33]# ./a.out Enter the filename: ita.txt Page | 37 #include<string.h> #include<sys/stat.h> #include<arpa/inet.h> #include<unistd.h> int main(int argc,char* argv[]) { int sd,size; char buff[1024],file[10000]; struct sockaddr_in cliaddr,servaddr; FILE *fp; struct stat x; socklen_t clilen; clilen=sizeof(cliaddr); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(9976); sd=socket(AF_INET,SOCK_DGRAM,0); if(sd<0) { printf("Socket CReation Error"); } bind(sd,(struct sockaddr *)&servaddr,sizeof(servaddr)); while(1) { bzero(buff,sizeof(buff)); recvfrom(sd,buff,sizeof(buff),0,(struct sockaddr *)&cliaddr,&clilen); strcat(buff,">file1"); system(buff); fp=fopen("file1","r"); stat("file1",&x); size=x.st_size; fread(file,size,1,fp); sendto(sd,file,sizeof(file),0,(struct sockaddr *)&cliaddr,sizeof(cliaddr)); printf("Data Sent to UDPCLIENT %s",buff); } close(sd); return 0; } Client: udpremoteclient.c #include<sys/types.h> #include<sys/socket.h> #include<stdio.h> #include<unistd.h> #include<netdb.h> #include<netinet/in.h> #include<string.h> #include<arpa/inet.h> #include<sys/stat.h> int main(int argc,char* argv[]) { Page | 40 int sd; char buff[1024],file[10000]; struct sockaddr_in cliaddr,servaddr; struct hostent *h; socklen_t servlen; servlen=sizeof(servaddr); h=gethostbyname(argv[1]); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=h->h_addrtype; memcpy((char *)&servaddr.sin_addr,h->h_addr_list[0],h->h_length); servaddr.sin_port=htons(9976); sd=socket(AF_INET,SOCK_DGRAM,0); if(sd<0) { printf("Socket CReation Error"); } bind(sd,(struct sockaddr *)&servaddr,sizeof(servaddr)); while(1) { printf("\nEnter the command to be executed"); fgets(buff,1024,stdin); sendto(sd,buff,strlen(buff)+1,0,(struct sockaddr *)&servaddr,sizeof(servaddr)); printf("\nData Sent"); recvfrom(sd,file,strlen(file)+1,0,(struct sockaddr *)&servaddr,&servlen); printf("Recieved From UDPSERVER %s",file); } return 0; } SAMPLE OUTPUT: Server: (Host Name:Root1) [root@localhost 4ita33]# vi udpremoteserver.c [root@localhost 4ita33]# cc udpremoteserver.c [root@localhost 4ita33]# ./a.out Server is running............ VIM(1) VIM(1) NAME vim - Vi IMproved, a programmers text editor SYNOPSIS vim [options] [file ..] vim [options] - vim [options] -t tag vim [options] -q [errorfile} ex review rview renbjc Page | 41 Client: (Host Name:Root2) [root@localhost 4ita33]# vi udpremoteclient.c [root@localhost 4ita33]# cc udpremoteclient.c [root@localhost 4ita33]# ./a.out 127.0.0.1 Enter command: man vi Command sent to server Enter command: INFERENCE: Thus the Remote Command Execution between the client and server is implemented. Page | 42