A simple time to get the client program

Program execution Flow:

1. Creating sockets

sockfd = socket(AF_INET, SOCK_STREAM, 0)

2. Zeroing the structure servaddr

bzero(&servaddr, sizeof(servaddr))

3. Place the address cluster asAF_INET

servaddr.sin_family = AF_INET

4. Port number set to 13

IP address and port number in an internetwork socket address structure These 2 members must use a specific format

Htons host to network short integer, to convert binary port number

servaddr.sin_port   = htons(13)

5. Transform the ASCII dot decimal string (IP address) into the correct format

inet_pton(AF_INET, argv[1], &servaddr.sin_addr)

6. Establish a connection to the server

connect(sockfd, (SA *) &servaddr, sizeof(servaddr))

Establishes a TCP connection with the server specified by the socket address structure that the first parameter of the Connect function points to

The length of the socket address structure must also be specified as the third parameter of the function

#define SA struct SOCKADDR is the universal socket address structure

7. Read the server's response

n = read(sockfd, recvline, MAXLINE)

Because there is no guarantee that a read call can return the entire answer to the server, when reading data from a TCP socket, we always need to write read in a loop, and when read returns 0 to close the connection to the end, a negative value indicates a dislocation, both terminating the loop.

8. Output results

fputs(recvline, stdout)


9. Termination procedures

exit(0)

#include "unp.h" intmain (int argc, char **argv) {INTSOCKFD, n;charrecvline[maxline + 1];struct sockaddr_inservaddr;if ( ARGC! = 2) err_quit ("Usage:a.out <IPaddress>"); if (SOCKFD = socket (af_inet, sock_stream, 0)) < 0) Err_sys ("Socke T error "); Bzero (&servaddr, sizeof (SERVADDR)); servaddr.sin_family = Af_inet;servaddr.sin_port   = htons (13);/* Daytime server */if (Inet_pton (Af_inet, argv[1], &servaddr.sin_addr) <= 0) err_quit ("Inet_pton error for%s", argv[ 1]); if (Connect (SOCKFD, (SA *) &servaddr, sizeof (SERVADDR)) < 0) Err_sys ("Connect Error"), while (n = Read (SOCKFD, Recvline, MAXLINE)) > 0) {recvline[n] = 0;/* null terminate */if (fputs (recvline, stdout) = = EOF) Err_sys ("Fputs error") ;} if (n < 0) Err_sys ("read error"); exit (0);}

A simple time to get the client program