TCP Daytime implementation using C

In the following program, we will demonstrate, how a connection can be established between client and server using Transport Layer Protocol - TCP. This code is self-explanatory. Hence, first, you will learn to develop server-side applications. Then, you will learn to develop client-side applications.

First, define a header file "unp.h" as follow. We will use this header file in other programs.

#include <sys/types.h> #include <sys/socket.h> #include <sys/time.h> #include <time.h> #include <netinet/in.h> #include <arpa/inet.h> #include <errno.h> #include <fcntl.h> #include <netdb.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <strings.h> #include <string.h> #include <sys/stat.h> #include <sys/uio.h> #include <unistd.h> #include <sys/wait.h> #include <sys/un.h> #define MAXLINE 4096 #define LISTENQ 2

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Source Code of the echo server

#include <stdio.h> #include <time.h> #include "unp.h" int main(int argc, char *argv[]) { pid_t p, q; int listen_file_descriptor, connfd; struct sockaddr_in server_address; char buffer[MAXLINE]; time_t clock_tick; listen_file_descriptor = socket(AF_INET, SOCK_STREAM, 0); bzero(&server_address, sizeof(server_address)); server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = htonl(INADDR_ANY); server_address.sin_port = htons(8000); bind(listen_file_descriptor, (struct sockaddr *)&server_address, sizeof(server_address)); listen(listen_file_descriptor, LISTENQ); while(1) { connfd = accept(listen_file_descriptor, (struct sockaddr *)NULL, NULL); p = fork(); if(p == 0) { q = getpid(); printf("%d", &q); close(listen_file_descriptor); clock_tick = time(NULL); snprintf(buffer, sizeof(buffer), "%.24s\r\n", ctime(&clock_tick)); write(connfd, buffer, strlen(buffer)); close(connfd); exit(0); } close(connfd); } }

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Source Code of the echo Client 

#include <stdio.h> #include "unp.h" int main(int argc,char *argv[]) { int socket_file_descriptor, n; char recvline[MAXLINE+1]; struct sockaddr_in server_address; if(argc!=2) { printf("usage:client <IPaddress>"); exit(0); } if ((socket_file_descriptor = socket(AF_INET, SOCK_STREAM, 0)) < 0) printf("socket error"); bzero(&server_address, sizeof(server_address)); server_address.sin_family = AF_INET; server_address.sin_port = htons(8000); if((server_address.sin_addr.s_addr = inet_addr(argv[1])) <= 0) { printf("inet_pton error for %s", argv[1]); exit(0); } if(connect(socket_file_descriptor,(struct sockaddr *) &server_address, sizeof(server_address)) < 0) printf("connect error"); while((n = read(socket_file_descriptor,recvline,MAXLINE)) > 0) { recvline[n] = 0; if(fputs(recvline, stdout) == EOF) printf("fputs error"); } if(n < 0) printf("read error"); exit(0); }

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Happy Exploring!