书本P260例7.3中
server如果被第二次启动，就会出现如下错误：
bind：Address already in use
解决方案如下：
首先删除所有的.o文件，然后对
server代码修改如下：
#include <sys/types.h>
#include <sys/socket.h>#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/wait.h>
#include <string.h>
#include <errno.h>
#define DEFAULT_PORT 6666
int main( int argc, char ** argv){
int serverfd,acceptfd; /* 监听socket: serverfd,数据传输socket: acceptfd */
struct sockaddr_in my_addr; /* 本机地址信息 */
struct sockaddr_in their_addr; /* 客户地址信息 */
unsigned int sin_size, myport=6666, lisnum=10;
if ((serverfd = socket(AF_INET , SOCK_STREAM, 0)) == -1) {
perror("socket" );
return -1;
}
printf("socket ok \n");
my_addr.sin_family=AF_INET;
my_addr.sin_port=htons(DEFAULT_PORT);
my_addr.sin_addr.s_addr = INADDR_ANY;
int on=1;
if((setsockopt(serverfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on)))<0)
{
perror("setsockopt failed");
exit(EXIT_FAILURE);
}
bzero(&(my_addr.sin_zero), 0);
if (bind(serverfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr )) == -1) {
perror("bind" );
return -2;
}
printf("bind ok \n");
if (listen(serverfd, lisnum) == -1) {
perror("listen" );
return -3;
}
printf("listen ok \n");
fd_set client_fdset; /*监控文件描述符集合*/
int maxsock; /*监控文件描述符中最大的文件号*/
struct timeval tv; /*超时返回时间*/
int client_sockfd[5]; /*存放活动的sockfd*/
bzero((void*)client_sockfd,sizeof(client_sockfd));
int conn_amount = 0; /*用来记录描述符数量*/
maxsock = serverfd;
char buffer[1024];
int ret=0;
while(1){
/*初始化文件描述符号到集合*/
FD_ZERO(&client_fdset);
/*加入服务器描述符*/
FD_SET(serverfd,&client_fdset);
/*设置超时时间*/
tv.tv_sec = 30; /*30秒*/
tv.tv_usec = 0;
/*把活动的句柄加入到文件描述符中*/
for(int i = 0; i < 5; ++i){
/*程序中Listen中参数设为5,故i必须小于5*/
if(client_sockfd[i] != 0){
FD_SET(client_sockfd[i], &client_fdset);
}
}
/*printf("put sockfd in fdset!\n");*/
/*select函数*/
ret = select(maxsock+1, &client_fdset, NULL, NULL, &tv);
if(ret < 0){
perror("select error!\n");
break;
}
else if(ret == 0){
printf("timeout!\n");
continue;
}
/*轮询各个文件描述符*/
for(int i = 0; i < conn_amount; ++i){
/*FD_ISSET检查client_sockfd是否可读写，>0可读写*/
if(FD_ISSET(client_sockfd[i], &client_fdset)){
printf("start recv from client[%d]:\n",i);
ret = recv(client_sockfd[i], buffer, 1024, 0);
if(ret <= 0){
printf("client[%d] close\n", i);
close(client_sockfd[i]);
FD_CLR(client_sockfd[i], &client_fdset);
client_sockfd[i] = 0;
}
else{
printf("recv from client[%d] :%s\n", i, buffer);
}
}
}
/*检查是否有新的连接，如果收，接收连接，加入到client_sockfd中*/
if(FD_ISSET(serverfd, &client_fdset)){
/*接受连接*/
struct sockaddr_in client_addr;
size_t size = sizeof(struct sockaddr_in);
int sock_client = accept(serverfd, (struct sockaddr*)(&client_addr), (unsigned int*)(&size));
if(sock_client < 0){
perror("accept error!\n");
continue;
}
/*把连接加入到文件描述符集合中*/
if(conn_amount < 5){
client_sockfd[conn_amount++] = sock_client;
bzero(buffer,1024);
strcpy(buffer, "this is server! welcome!\n");
send(sock_client, buffer, 1024, 0);
printf("new connection client[%d] %s:%d\n", conn_amount, inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
bzero(buffer,sizeof(buffer));
ret = recv(sock_client, buffer, 1024, 0);
if(ret < 0){
perror("recv error!\n");
close(serverfd);
return -1;
}
printf("recv : %s\n",buffer);
if(sock_client > maxsock){
maxsock = sock_client;
}
else{
printf("max connections!!!quit!!\n");
break;
}
}
}
}
for(int i = 0; i < 5; ++i){
if(client_sockfd[i] != 0){
close(client_sockfd[i]);
}
}
printf("serverfd = %d\n",serverfd);
printf("acceptfd = %d\n",acceptfd);
close(serverfd);
return 0;
}
client代码不变
然后对server和client代码进行重新编译即可