用select实现TCP回射程序（服务器及客户端）

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/select.h>
#include <string.h>
#include <strings.h>
#include <errno.h>

#define PORT 8888
#define BACKLOG 100
#define MAXLINE 1024

int main() {
int listenfd, connfd, sockfd;
int client[FD_SETSIZE];
int i, n;
struct sockaddr_in servaddr, cliaddr;
socklen_t clilen;
fd_set rset, allset;
int maxfd, maxcli;
int nready;
char buf[MAXLINE];

//创建监听套接字
if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
printf("socket error\n");
exit(1);
}

//写入套接字地址
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(PORT);

//绑定地址
if ((n = bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr))) < 0) {
printf("bind error\n");
exit(1);
}

//监听
if ((n = listen(listenfd, BACKLOG)) < 0) {
printf("listen error\n");
exit(1);
}

for (i = 0; i < FD_SETSIZE; i++)
client[i] = -1;
maxfd = listenfd;
maxcli = -1;
FD_ZERO(&allset);
FD_SET(listenfd, &allset);

for (;;) {
rset = allset;

if ((nready = select(maxfd + 1, &rset, NULL, NULL, NULL)) < 0) {
printf("select error\n");
printf("%s\n", strerror(errno));
exit(1);
}

if (FD_ISSET(listenfd, &rset)) {
//接受新连接
if ((connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen)) < 0) {
printf("accept error\n");
exit(1);
}
printf("accept: %d\n", connfd);

//更新连接表
for (i = 0; i < FD_SETSIZE; i++)
if (client[i] < 0) {
client[i] = connfd;
break;
}

FD_SET(connfd, &allset); //更新描述符集

if (connfd > maxfd)
maxfd = connfd; //更新最大文件描述符

if (i > maxcli)
maxcli = i; //更新最大连接表索引

if (--nready <= 0)
continue;
}

for (i = 0; i <= maxcli; i++) {
if ((sockfd = client[i]) < 0)
continue;
if (FD_ISSET(sockfd, &rset)) {
if ((n = read(sockfd, buf, MAXLINE)) == 0) {
if (close(sockfd) < 0) {
printf("close error\n");
exit(1);
}
printf("close: %d\n", sockfd);
FD_CLR(sockfd, &allset);
client[i] = -1;
} else {
if (n < 0) {
printf("read error\n");
exit(0);
}
if (n > 0) {
if (write(sockfd, buf, n) < 0) {
printf("write error\n");
exit(1);
}
}
}
if (--nready <= 0)
break;
}
}
}
}

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

#define PORT 8888
#define MAXLINE 1024

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

if(argc != 2){
printf("invalid usage!\n");
exit(1);
}

if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
printf("socket error!\n");
exit(1);
}

servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(PORT);
if((n = inet_pton(AF_INET,  argv[1], &servaddr.sin_addr)) < 0){
printf("pton error\n");
exit(1);
}
else if(n == 0){
printf("invalid ip\n");
exit(1);
}

if((n = connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr))) < 0){
printf("connect error\n");
exit(1);
}

maxfd = sockfd;
FD_ZERO(&rset);
stdineof = 0;

for(;;){
if(stdineof == 0)
FD_SET(0, &rset);
FD_SET(sockfd, &rset);

if((n = select(maxfd+1, &rset, NULL, NULL, NULL)) < 0){
printf("select error\n");
exit(1);
}

if(FD_ISSET(0, &rset)){
if((n = read(0, buf, MAXLINE)) == 0){
stdineof = 1;
if(shutdown(sockfd, SHUT_WR) < 0){
printf("shutdown error\n");
exit(1);
}
FD_CLR(0, &rset);
continue;
}
else if(n < 0){
printf("stdin read error\n");
exit(1);
}
if((n = write(sockfd, buf, n)) < 0){
printf("socket write error\n");
exit(1);
}
}

if(FD_ISSET(sockfd, &rset)){
if((n = read(sockfd, buf, MAXLINE)) == 0){
if(stdineof == 1)
break;
else{
printf("server terminated\n");
exit(1);
}
}
else if(n < 0){
printf("socket read error\n");
exit(1);
}
if((n = write(1, buf, n)) < 0){
printf("stdout write error\n");
exit(1);
}
}
}
return 0;
}