TCP-server/client实现字符大写转换

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

#define MAXLINE 80
#define SERV_PORT 6666

void* thread_routine(void* arg){
char buf[MAXLINE];
int n = 0;
int i;
int connfd = (int)arg;
while(1){
n = read(connfd,buf,MAXLINE);
if(n == 0){
break;
}else if( strncmp(buf,"exit",4) == 0 ){
break;
}else{
for(i = 0 ; i < n ; ++i){
buf[i] = toupper(buf[i]);
}
write(connfd,buf,n);
}
}
printf("client id: %lu bye\n",pthread_self());
close(connfd);
pthread_exit(NULL);
}

int main(void)
{
struct sockaddr_in servaddr, cliaddr;
socklen_t cliaddr_len;
int listenfd, connfd;
char str[INET_ADDRSTRLEN];
int i, n;
pthread_t thread_id;
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(SERV_PORT);

bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
listen(listenfd, 20);

while (1) {

printf("Accepting connections ...\n");
cliaddr_len = sizeof(cliaddr);
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
//n = read(connfd, buf, MAXLINE);
printf("received from %s at PORT %d\n",
inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
ntohs(cliaddr.sin_port));
if( 0 != pthread_create(&thread_id,NULL,thread_routine,(void*)connfd)){
exit(1);
}
pthread_detach(thread_id);
}
close(listenfd);
return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define MAXLINE 100
#define SERV_PORT 6666

int main(int argc, char *argv[])
{
struct sockaddr_in servaddr;
char buf[MAXLINE];
int sockfd, n;
char sendbuf[MAXLINE];

sockfd = socket(AF_INET, SOCK_STREAM, 0);

bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
servaddr.sin_port = htons(SERV_PORT);

connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

while(1){

write(STDOUT_FILENO,"send toserver:",strlen("send toserver:"));
n = read(STDIN_FILENO,sendbuf,MAXLINE);
if(n == 0){
printf("read error\n");
}

write(sockfd, sendbuf, n);
if(0 == strncmp(sendbuf,"exit",4)){
break;
}
n = read(sockfd, buf, MAXLINE);
write(STDOUT_FILENO,"Response from server:",strlen("Response from server:"));
write(STDOUT_FILENO, buf, n);
}
close(sockfd);
printf("bye\n");
return 0;
}