Det her er sikkert ikke jordens bedste eksempel.
Men det illusterer den rimeligt lille fordel mellem blocking og non-blocking
client.
Eksemplet henter en side via HTTP.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <netdb.h>
#include <errno.h>
void get(char *hostname,int port,char *path,int noblock)
{
int sd,status,len,ix,tmp;
char cmd[512],resp[51200];
struct sockaddr local,remote;
struct hostent *hostinfo;
time_t t;
/* create socket */
sd=socket(AF_INET,SOCK_STREAM,0);
if(sd<0) {
printf("Error creating socket: %s\n",strerror(errno));
goto fin;
}
/* bind socket */
local.sa_family=AF_INET;
memset(local.sa_data,0,sizeof(local.sa_data));
status=bind(sd,&local,sizeof(local));
if(status<0) {
printf("Error binding socket: %s\n",strerror(errno));
goto fin;
}
/* lookup host */
hostinfo=gethostbyname(hostname);
if(!hostinfo) {
printf("Error looking up host: %s\n",hostname);
goto fin;
}
/* connect to host */
remote.sa_family=hostinfo->h_addrtype;
memcpy(remote.sa_data+2,hostinfo->h_addr_list[0],hostinfo->h_length);
*((short *)remote.sa_data)=port;
tmp=remote.sa_data[0];
remote.sa_data[0]=remote.sa_data[1];
remote.sa_data[1]=tmp;
status=connect(sd,&remote,sizeof(remote));
if(status!=0) {
printf("Error connecting to host: %s port: %d\n",hostname,port);
goto fin;
}
/* send GET request */
sprintf(cmd,"GET %s HTTP/1.1\r\nHost: %s\r\n\r\n",path,hostname);
status=send(sd,cmd,strlen(cmd),0);
if(status<0) {
printf("Error sending POST request\n");
goto fin;
}
/* read response */
ix=0;
if(noblock) {
status=fcntl(sd,F_SETFL,O_NONBLOCK);
if(status<0) {
printf("Error setting socket nonblocked: %s\n",strerror(errno));
goto fin;
}
t=time(NULL);
while (time(NULL)<(t+5)) {
len=recv(sd,resp+ix,sizeof(resp)-ix-1,0);
ix = ix + len;
printf("no blocking read %d bytes\n",len);
sleep(1);
}
} else {
while ((len=recv(sd,resp+ix,sizeof(resp)-ix-1,0))>0) {
ix = ix + len;
printf("blocking read %d bytes\n",len);
}
}
resp[ix]='\0';
/*printf("%s",resp);*/
fin:
close(sd);
return;
}
int main(int argc,char *argv[])
{
get("
www.xxx.dk",80,"/",0);
get("
www.xxx.dk",80,"/",1);
}
Output på minLinux box:
blocking read 241 bytes
blocking read 1460 bytes
blocking read 72 bytes
no blocking read -1 bytes
no blocking read 1773 bytes
no blocking read 0 bytes
no blocking read 0 bytes
