Linux socket编程实战（非阻塞）

socket在创建的时候默认是阻塞的，要想设置为非阻塞的有以下几种方法：

1.ioctl 和 fcntl 设置已经创建socket的fd

ioctl用于设备控制

  #include <sys/ioctl.h>

  int ioctl(int fd, unsigned long request, ...);

fcntl用于文件控制 

 #include <unistd.h>
 #include <fcntl.h>

 int fcntl(int fd, int cmd, ... /* arg */ );

通过下面方式设置：

flags = fcntl(sfd, F_GETFL);
flags |= O_NONBLOCK;
fcntl(sfd, F_SETFL, flags);

2.在创建socket的时候设置

int fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);

3.accept4

int accept4(int sockfd, struct sockaddr *addr,socklen_t *addrlen, int flags);

   flags 设置成 SOCK_NONBLOCK，这种方式是在服务端。

服务端设置5秒后再接收数据：

#include<sys/socket.h>
#include<sys/types.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdio.h>
#include<errno.h>


int main(int argc, char* argv[]){

int fd = socket(AF_INET, SOCK_STREAM, 0);
if(fd < 0){
	printf("create socket failed!, errno=%d\n",errno);
}
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(8080);

int ret;
ret = bind(fd, (struct sockaddr*) &addr, sizeof(addr));
if(ret == -1){
	printf("bind failed!, errno=%d",errno);
	close(fd);
}
ret = listen(fd, SOMAXCONN);
if(ret == -1){
	printf("listen failed!, errno=%d",errno);
}
struct sockaddr_in clientaddr;
socklen_t clientaddrlen = sizeof(clientaddr);
int afd = accept(fd, (struct sockaddr*) &clientaddr, &clientaddrlen);
if(afd != -1){
	printf("A client connected!,ip=%s,port=%d\n",inet_ntoa(clientaddr.sin_addr), ntohs(clientaddr.sin_port));
	char buf[256] = {0};
    sleep(5);
	ret = recv(afd, buf, 256, 0);
	if(ret > 0){
		printf("recv %d byte:%s\n",ret,buf);
	}
	else if(ret == -1){
		printf("recv error!,errno=%d\n",errno);
	}
	else{
		printf("client disconnect!\n");
	}	
}
else{
	printf("accept failed!,errno=%d\n",errno);
}
}

 客户端设置非阻塞，验证一下send非阻塞的现象：

#include<sys/socket.h>
#include<sys/types.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdio.h>
#include <stdlib.h>
#include<errno.h>
#include<string.h>
#include <fcntl.h>

int main(int argc, char* argv[]){
	

if(argc != 3){
	printf("please input IP port\n");
}
char* ip = argv[1];
unsigned int port = atoi(argv[2]);
int fd = socket(AF_INET, SOCK_STREAM, 0);
if(fd < 0){
	printf("create socket failed!, errno=%d\n",errno);
}
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(ip);
addr.sin_port = htons(port);

int ret;
ret = connect(fd, (struct sockaddr*) &addr, sizeof(addr));
if(ret == -1){
	printf("connect failed!, errno=%d",errno);
}
else{
	//连接成功后将fd设置为非阻塞
	int flags = fcntl(fd, F_GETFL);
    flags |= O_NONBLOCK;
    ret = fcntl(fd, F_SETFL, flags);
	if(ret == -1){
		printf("set O_NONBLOCK failed!,errno=%d\n",errno);
	}
	char *buf = "hello, I am a client!";
	int cnt = 0;
	while(1){
			ret = send(fd, buf, strlen(buf), 0);
			if(ret > 0){
				cnt++;
				printf("send %d byte:%s,cnt = %d\n",ret,buf,cnt);
			}
			else if(ret == -1){
				if(errno == EAGAIN){
					printf("send try again\n");
					sleep(1);
					continue;
				}
				else
				printf("send error!,errno=%d\n",errno);
			}
			else{
				printf("server disconnect!\n");
			}
	}
	
}
	
}