c

#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>#define PORT 20000#define MAXDATASIZE 100 int main(int argc, char *argv[]){    int sockfd, numbytes;    int len;    char buf[MAXDATASIZE];    struct hostent *he;    struct sockaddr_in their_addr;     if (argc != 2) {        fprintf(stderr,"usage: client hostname\n");        exit(1);    }    if ((he=gethostbyname(argv[1])) == NULL) {        herror("gethostbyname");        exit(1);    }    if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {        perror("socket");        exit(1);    }    their_addr.sin_family = AF_INET;     their_addr.sin_port = htons(PORT);     their_addr.sin_addr = *((struct in_addr *)he->h_addr);    memset(&(their_addr.sin_zero), '\0', 8);    if (connect(sockfd, (struct sockaddr *)&their_addr,                                          sizeof(struct sockaddr)) == -1) {        perror("connect");        exit(1);    }while (strcmp(buf, ".")) {    if ((numbytes=recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {        perror("recv");        exit(1);    }    buf[numbytes] = '\0';    printf("%s\n", buf);printf("Input: ", str);scanf("%s", str);len = strlen("%s");send(sockfd, "SAY lol", len, 0);}    return 0;}