uDP ECHO:

STEP 1: Start
    STEP 2: Declare the variables for the socket
    STEP 3: Specify the family, protocol, IP address and port number
    STEP 4: Create a socket using socket() function
    STEP 5: Bind the IP address and Port number
    STEP 6: Listen and accept the client’s request for the connection
    STEP 7: Read and Display the client’s message
    STEP 8: Stop
CLIENT:
    STEP 1: Start
    STEP 2: Declare the variables for the socket
    STEP 3:  Specify the family, protocol, IP address and port number
    STEP 4: Create a socket using socket() function
    STEP 5: Call the connect() function
    STEP 6: Read the input message
    STEP 7: Send the input message to the server
    STEP 8: Display the server’s echo
    STEP 9: Close the socket
    STEP 10: Stop

SOURCE CODE:
SERVER:
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<unistd.h>
#include<netdb.h>
#include<stdio.h>
#include<string.h>
#include<arpa/inet.h>
#define MAXLINE 1024
int main(int argc,char **argv)
{
int sockfd;
int n;
socklen_t len;
char msg[1024];
struct sockaddr_in servaddr,cliaddr;
sockfd=socket(AF_INET,SOCK_DGRAM,0);
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=INADDR_ANY;
servaddr.sin_port=htons(5035);
printf("\n\n Binded");
bind(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));
printf("\n\n Listening...");
for(;;)
{
      printf("\n ");
     len=sizeof(cliaddr);
     n=recvfrom(sockfd,msg,MAXLINE,0,(struct sockaddr*)&cliaddr,&len);
     printf("\n Client's Message : %s\n",msg);
     if(n<6)
        perror("send error");
     sendto(sockfd,msg,n,0,(struct sockaddr*)&cliaddr,len);
}
return 0;
}

CLIENT:
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<string.h>
#include<arpa/inet.h>
#include<string.h>
#include<arpa/inet.h>
#include<stdio.h>
#define MAXLINE 1024
int main(int argc,char* argv[])
{
int sockfd;
int n;
socklen_t len;
char sendline[1024],recvline[1024];
struct sockaddr_in servaddr;
strcpy(sendline,"");
printf("\n Enter the message : ");
scanf("%s",sendline);
sockfd=socket(AF_INET,SOCK_DGRAM,0);
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=htons(5035);
connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));
len=sizeof(servaddr);
sendto(sockfd,sendline,MAXLINE,0,(struct sockaddr*)&servaddr,len);
n=recvfrom(sockfd,recvline,MAXLINE,0,NULL,NULL);
recvline[n]=0;
printf("\n Server's Echo : %s\n\n",recvline);
return 0;
}

UDP message:
Server:

#include<sys/socket.h>
#include<arpa/inet.h>
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<string.h>




int main()
{

  char buff[2000];
  char file_buffer[2000];
  int sd,connfd,len;

  struct sockaddr_in servaddr,cliaddr;

  sd = socket(AF_INET, SOCK_DGRAM, 0);

  if(sd==-1)
    {
      printf(" socket not created in server\n");
      exit(0);
    }
  else
    {
      printf("socket created in  server\n");
    }

  bzero(&servaddr, sizeof(servaddr));

  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = INADDR_ANY;
  servaddr.sin_port = htons(7802);

  if ( bind(sd, (struct sockaddr *)&servaddr, sizeof(servaddr)) != 0 )
    printf("Not binded\n");
  else
    printf("Binded\n");



  len=sizeof(cliaddr);

  recvfrom(sd,buff,1024,0,
   (struct sockaddr *)&cliaddr, &len);

  printf("%s\n",buff);
  /* */
  FILE *fp;
  fp=fopen(buff,"r");
  if(fp==NULL)
    {
      printf("file does not exist\n");
    }

  fseek(fp,0,SEEK_END);
  size_t file_size=ftell(fp);
  fseek(fp,0,SEEK_SET);
  if(fread(file_buffer,file_size,1,fp)<=0)
    {
      printf("unable to copy file into buffer\n");
      exit(1);
    }
  if(sendto(sd,file_buffer,strlen(file_buffer),0,  (struct sockaddr *)&cliaddr, &len)<0)    {
    printf("error in sending the file\n");
    exit(1);
  }
  bzero(file_buffer,sizeof(file_buffer));


  /* */
  close(sd);

  return(0);
}

Client:
#include <stdio.h>
#include <errno.h>
#include <sys/socket.h>
#include <resolv.h>
#include<netinet/in.h>
#include<sys/types.h>



int main()
{
    char buff[2000];
    int sockfd,connfd,len;

struct sockaddr_in servaddr,cliaddr;

// create socket in client side
sockfd = socket(AF_INET, SOCK_DGRAM, 0);

if(sockfd==-1)
{
    printf(" socket not created in client\n");
    exit(0);
}
else
{
    printf("socket created in  client\n");
}


bzero(&servaddr, sizeof(servaddr));

servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = INADDR_ANY; // ANY address or use specific address
servaddr.sin_port = htons(7802);  // Port address


    printf("Type ur  UDP client message\n");
    scanf("%s",buff);

// send  msg to server

sendto(sockfd, buff, strlen(buff), 0,
          (struct sockaddr *)&servaddr, sizeof(struct sockaddr));
      char file_buffer[2000];

    if (recvfrom(sockfd,file_buffer,2000,0,  (struct sockaddr *)&servaddr, sizeof(struct sockaddr))<0)
    {
      printf("error in recieving the file\n");
      exit(1);
    }

  char new_file[]="copied";
  strcat(new_file,buff);
  FILE *fp;
  fp=fopen(new_file,"w+");
  if(fwrite(file_buffer,1,sizeof(file_buffer),fp)<0)
    {
      printf("error writting file\n");
      exit(1);
    }


  //close client side connection
    close(sockfd);

return(0);
}


tcp/ip chat:

SERVER
#include<stdio.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netdb.h>
#include<stdlib.h>
#include<string.h>
#define MAX 80
#define PORT 43454
#define SA struct sockaddr
void func(int sockfd)
{
char buff[MAX];
int n;
for(;;)
{
bzero(buff,MAX);
read(sockfd,buff,sizeof(buff));
printf("From client: %s\t To client : ",buff);
bzero(buff,MAX);
n=0;
while((buff[n++]=getchar())!='\n');
write(sockfd,buff,sizeof(buff));
if(strncmp("exit",buff,4)==0)
{
printf("Server Exit...\n");
break;
}
}
}
int main()
{
int sockfd,connfd,len;
struct sockaddr_in servaddr,cli;
sockfd=socket(AF_INET,SOCK_STREAM,0);
if(sockfd==-1)
{
printf("socket creation failed...\n");
exit(0);
}
else
printf("Socket successfully created..\n");
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
servaddr.sin_port=htons(PORT);
if((bind(sockfd,(SA*)&servaddr, sizeof(servaddr)))!=0)
{
printf("socket bind failed...\n");
exit(0);
}
else
printf("Socket successfully binded..\n");
if((listen(sockfd,5))!=0)
{
printf("Listen failed...\n");
exit(0);
}
else
printf("Server listening..\n");
len=sizeof(cli);
connfd=accept(sockfd,(SA *)&cli,&len);
if(connfd<0)
{
printf("server acccept failed...\n");
exit(0);
}
else
printf("server acccept the client...\n");
func(connfd);
close(sockfd);
}

CLIENT
#include<stdio.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netdb.h>
#include<string.h>
#include<stdlib.h>
#define MAX 80
#define PORT 43454
#define SA struct sockaddr
void func(int sockfd)
{
char buff[MAX];
int n;
for(;;)
{
bzero(buff,sizeof(buff));
printf("Enter the string : ");
n=0;
while((buff[n++]=getchar())!='\n');
write(sockfd,buff,sizeof(buff));
bzero(buff,sizeof(buff));
read(sockfd,buff,sizeof(buff));
printf("From Server : %s",buff);
if((strncmp(buff,"exit",4))==0)
{
printf("Client Exit...\n");
break;
}
}
}

int main()
{
int sockfd,connfd;
struct sockaddr_in servaddr,cli;
sockfd=socket(AF_INET,SOCK_STREAM,0);
if(sockfd==-1)
{
printf("socket creation failed...\n");
exit(0);
}
else
printf("Socket successfully created..\n");
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=htons(PORT);
if(connect(sockfd,(SA *)&servaddr,sizeof(servaddr))!=0)
{
printf("connection with the server failed...\n");
exit(0);
}
else
printf("connected to the server..\n");
func(sockfd);
close(sockfd);
}


tcp file transfer:
filetransferserver.c
#include<stdio.h>
#include<sys/types.h>
#include<string.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>
#define SA struct sockaddr
#define LISTENQ 5
int main(int argc,char**argv)
{
int fd,sockfd,listenfd,connfd;
pid_t childpid;
socklen_t client;
struct sockaddr_in servaddr,cliaddr;
listenfd=socket(AF_INET,SOCK_STREAM,0);
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
servaddr.sin_port=htons(atoi(argv[1]));
bind(listenfd,(SA*)&servaddr,sizeof(servaddr));
listen(listenfd,LISTENQ);
client=sizeof(cliaddr);
connfd=accept(listenfd,(SA*)&cliaddr,&client);
char buffer[100];
FILE *fp;
read(connfd,buffer,100);
fp=fopen("add1.txt","w");
fprintf(fp,"%s",buffer);
printf("the file was received successfully");
printf("the new file created is add1.txt");
}

iletransferclient.c
#include<arpa/inet.h>
#include<unistd.h>
#define SA struct sockaddr
int main(int argc,char**argv)
{
int sockfd;
char fname[25];
int len;
struct sockaddr_in servaddr,cliaddr;
sockfd=socket(AF_INET,SOCK_STREAM,0);
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
servaddr.sin_port=htons(atoi(argv[1]));
inet_pton(AF_INET,argv[1],&servaddr.sin_addr);
connect(sockfd,(SA*)&servaddr,sizeof(servaddr));
char buffer[100];
FILE *f;
f=fopen("add.txt","r");
fscanf(f,"%s",buffer);
write(sockfd,buffer,100);
printf("the file was sent successfully");
}

tcp/ip username pass
Server :
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
int main(int argc, char *argv[])
{
int sock_des,port,n1,n2,s1,s2;
char null_character;
char buffer1[100],buffer2[100],buffer3[100],buffer4[100];
int length,new_des;
struct sockaddr_in server_addr,client_addr;
bzero(buffer3,sizeof(buffer3));
printf("\n Input Authentic Username :\n");
scanf("%s",buffer3);
bzero(buffer4,sizeof(buffer4));
printf("\n Input Authentic Password :\n");
scanf("%s",buffer4);
if(argc!=2)
{
printf("Usage: ./server port\n");
exit(1);
}
port= atoi(argv[1]);
if((sock_des=socket(AF_INET,SOCK_STREAM,0))==-1)
{
perror("socket");
exit(1);
}

server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(port);
server_addr.sin_addr.s_addr= htonl(INADDR_ANY);
if (bind(sock_des,(const struct sockaddr *)&server_addr,sizeof(struct sockaddr))==-1)
{
perror("bind");
exit(1);
}
if( listen(sock_des,5)==-1)
{
perror("listen");
exit(1);
}
printf("Server is listening at port %d \n", port);
while(1)
{
if((new_des=accept(sock_des,(struct sockaddr *)&client_addr,&length))==-1)
{
perror("accept");
exit(1);
}
bzero(buffer1,sizeof(buffer1));
n1=read(new_des,buffer1,sizeof(buffer1));
buffer1[n1]=null_character;
if((s1=strcmp(buffer1,buffer3))==0)
{
write(new_des,"Username Match!Enter Password",30);
printf("Username Match !!!\n");
bzero(buffer2,sizeof(buffer2));
n2=read(new_des,buffer2,sizeof(buffer2));
buffer2[n2]=null_character;
if((s2=strcmp(buffer2,buffer4))==0)
{
write(new_des,"Password Match",15);
printf("Password Match !!!\n");
}
else
{
write(new_des,"Password NOT Match",19);
printf("Password NOT Match !!!\n");
}
}
else
{
write(new_des,"Username Not Match",19);
printf("Username Not Match !!!\n");
}
close(new_des);
}
}

Client :-

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
int main(int argc,char *argv[])
{
int sock_des,port,n;
char null_character;
struct hostent *host;
char buffer1[100],buffer2[100],buffer3[100],buffer4[100];
struct sockaddr_in server_addr;
if(argc!=3)
{
printf("Usage: ./client hostname port\n");
exit(1);
}
if((host=gethostbyname(argv[1]))==NULL)
{
printf("Unknown Host\n");
exit(1);
}
port = atoi(argv[2]);
if((sock_des=socket(AF_INET,SOCK_STREAM,0))==-1)
{
perror("socket");
exit(1);
}
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(port);
server_addr.sin_addr = *((struct in_addr *)host->h_addr);
if(connect(sock_des,(struct sockaddr *)&server_addr,sizeof(struct sockaddr))==-1)
{
perror("connect");
exit(1);
}
bzero(buffer1,sizeof(buffer1));
printf("Enter the Username :\n");
scanf("%s",buffer1);
write(sock_des,buffer1,sizeof(buffer1));
bzero(buffer4,sizeof(buffer4));

n=read(sock_des,buffer4,sizeof(buffer4));
buffer4[n]= null_character;
printf("Server Sent : %s\n", buffer4);
bzero(buffer2,sizeof(buffer2));
printf("Enter the Password :\n");
scanf("%s",buffer2);
write(sock_des,buffer2,sizeof(buffer2));
bzero(buffer3,sizeof(buffer3));
n=read(sock_des,buffer3,sizeof(buffer3));
buffer3[n]=null_character;
printf("Server Sent : %s\n", buffer3);
close(sock_des);
}



	for (i=0;i<7;i++) {
		printf("%d ",data[i]);
	}
	printf("\nenter the received data bits one by one: ");
	for (i=0;i<7;i++) {
		scanf("%d",&rec[i]);
	}
	c1=rec[6]^rec[4]^rec[2]^rec[0];
	c2=rec[5]^rec[4]^rec[1]^rec[0];
	c3=rec[3]^rec[2]^rec[1]^rec[0];
	c=c3*4+c2*2+c1 ;
	if(c==0) {
		printf("\ncongratulations there is no error: ");
	} else {
		printf("\nerron on the postion: %d\nthe correct message is \n",c);
		if(rec[7-c]==0)
					rec[7-c]=1; else
					rec[7-c]=0;
		for (i=0;i<7;i++) {
			printf("%d ",rec[i]);
		}
	}
	getch();
}



6.sliding window protocol-go back n arq
#include<iostream>
#include<math.h>
using namespace std;
int main()
{
    int m,ws,check=1,count=0;
    cout<<"enter the value of m"<<endl;       //what is m???
    cin>>m;
    //calculating window size
    ws=pow(2,m)-1;
    cout<<"ws= "<<ws<<endl;
    int sn=0,sf=0,rn=0,ack,time;
    cout<<"enter time out value "<<endl;
    cin>>time;
    while(check)
    {
    //cout<<sn<<" "<<ws<<endl;
        if(sn == ws)
            {
                cout<<"window full cannot enter anymore data"<<endl;
                break;
            }
        cout<<"press 1 to transmit data else press 0"<<endl;
        cin>>check;
        sn++;
        cout<<"press 1 if acknowledgement is received else press 0"<<endl;
        cin>>ack;
        if(ack)
            {
            rn++;
            sf++;
            time=3;
            }
        else
           {
            time--;
            if(time==0)
            {
            cout<<"time out transmit again from frame "<<sf<<endl;
            sn=sf;
            }
            }
            cout<<"data frames sent= "<<sn<<endl;
            cout<<"data frames received= "<<rn<<endl;
    }
}




7.client chat app using tcp ip
chatappserver.c
#include<sys/socket.h>
#include<sys/types.h>
#include<stdio.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<string.h>
#include<unistd.h>
#define SER_PORT 1200
int main()
{
int a,sersock,newsock,n;
char str[25],str2[25];
struct sockaddr_in seraddr;
struct sockaddr_in cliinfo;
socklen_t csize=sizeof(cliinfo);
seraddr.sin_family=AF_INET;
seraddr.sin_port=htons(SER_PORT);
seraddr.sin_addr.s_addr=htonl(INADDR_ANY);
if((sersock=socket(AF_INET,SOCK_STREAM,0))<0)
{
error("\n socket");
exit(0);
}
if(bind(sersock,(struct sockaddr *)&seraddr,sizeof(seraddr))<0)
{
error("\nBIND");
exit(0);
}
if(listen(sersock,1)<0)
{
error("\n LISTEN");
}
if((newsock=accept(sersock,(struct sockaddr *)&cliinfo,&csize))<0)
{
error("\n ACCEPT");
exit(0);
}
else
printf("\n now connected to %s\n",inet_ntoa(cliinfo.sin_addr));
read(newsock,str,sizeof(str));
do
{
printf("\n client msg:%s",str);
printf("\n server msg:");
scanf("%s",str2);
write(newsock,str2,sizeof(str2));
listen(newsock,1);
read(newsock,str,sizeof(str));
n=strcmp(str,"BYE");
a=strcmp(str2,"BYE");


}
while(n!=0||a!=0);
close(newsock);
close(sersock);
return 0;
}