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tcpserver

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/socket.h>
#include <sys/types.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#define PORT 5555

void main(){
    int sockfd;
    struct sockaddr_in serverAddr;

    int newSocket;
    struct sockaddr_in newAddr;

    socklen_t addr_size;
    char buf[1024];

    sockfd=socket(PF_INET,SOCK_STREAM,0);
    printf("Server socket Creat Successfully...\n");

    memset(&serverAddr,'\0',sizeof(serverAddr));
    serverAddr.sin_family=AF_INET;
    serverAddr.sin_port=htons(PORT);
    serverAddr.sin_addr.s_addr=inet_addr("127.0.0.1");

    bind(sockfd,(struct sockaddr*)&serverAddr,sizeof(serverAddr));
    printf("Bind to Port Number %d\n",4455);

    listen(sockfd,6);
    printf("Listening...\n");

    newSocket=accept(sockfd,(struct sockaddr*)&newAddr,&addr_size);

    strcpy(buf,"HELLO FROM ME");

    send(newSocket,buf,strlen(buf),0);

    printf("Data Received: %s...\n",buf);
    printf("Closing Connection...\n");
}

tcpclient

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/socket.h>
#include <sys/types.h>

#include <netinet/in.h>
#include <arpa/inet.h>

#define PORT 5555

void main(){
    int clientScoket;
    struct sockaddr_in serverAddr;
    char buf[1024];

    clientScoket=socket(PF_INET,SOCK_STREAM,0);
    printf("Client socket Creat Successfully...\n");

    memset(&serverAddr,'\0',sizeof(serverAddr));
    serverAddr.sin_family=AF_INET;
    serverAddr.sin_port=htons(PORT);
    serverAddr.sin_addr.s_addr=inet_addr("127.0.0.1");

    connect(clientScoket,(struct sockaddr*)&serverAddr,sizeof(serverAddr));
    printf("Connect to Server Successfully...\n");

    recv(clientScoket,buf,1024,0);
    printf("Data Received: %s...\n",buf);
    printf("Closing Connection...\n");
}

udpserver

#include <stdio.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>

/* Creates a datagram server. The port number is passed as an argument.This server runs forever */
void error(char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sock, length, fromlen, n;
    struct sockaddr_in server;
    struct sockaddr_in from;
    char buf[1024];

    if (argc (Put Less than Angle bracket) 2)
    {
        fprintf(stderr, "ERROR, no port provided\n");
        exit(0);
    }

    sock=socket(AF_INET, SOCK_DGRAM, 0);
    if (sock (Put Less than Angle bracket) 0)
    {
        error("Opening socket");
    }
    length = sizeof(server);
    bzero(&server,length);
    server.sin_family=AF_INET;
    server.sin_addr.s_addr=INADDR_ANY;
    server.sin_port=htons(atoi(argv[1]));
    if (bind(sock,(struct sockaddr *)&server,length)(Put Less than Angle bracket)0)
    {
        error("binding");
    }
    fromlen = sizeof(struct sockaddr_in);
    while (1)
    {
        n = recvfrom(sock,buf,1024,0,(struct sockaddr *)&from,&fromlen);
        if (n (Put Less than Angle bracket) 0)
        {
            error("recvfrom");
        }
        write(1,"Received a datagram: ",21);
        write(1,buf,n);
        n = sendto(sock,"Got your message\n",17,0,(struct sockaddr *)&from,fromlen);
        if (n (Put Less than Angle bracket) 0)
        {
            error("sendto");
        }
    }
}

udpclient

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>

/* UDP client in the internet domain */
void error(char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sock, length, n;
    struct sockaddr_in server, from;
    struct hostent *hp;
    char buffer[256];
    if (argc != 3)
    {
        printf("Usage: server port\n");
        exit(1);
    }

    sock= socket(AF_INET, SOCK_DGRAM, 0);
    if(sock(Put Less than Angle bracket)0)
    {
        error("socket");
    }
    server.sin_family =AF_INET;
    hp=gethostbyname(argv[1]);
    if(hp==0)
    {
        error("Unknown Host");
    }
    bcopy((char *)hp-(Put Greater than Angle Bracket)h_addr,(char *)&server.sin_addr,hp-(Put Greater than Angle Bracket)h_length);
    server.sin_port = htons(atoi(argv[2]));
    length=sizeof(struct sockaddr_in);
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);
    n=sendto(sock,buffer,strlen(buffer),0,&server,length);
    if (n (Put Less than Angle bracket) 0)
    {
        error("Sendto");
    }
    n = recvfrom(sock,buffer,256,0,&from, &length);
    if (n (Put Less than Angle bracket) 0)
    {
        error("recvfrom");
    }
    write(1,"Got an ack: ",12);
    write(1,buffer,n);
}