mini2440通过串口控制gms发送短信，请大神帮忙看看是我代码有问题还是什么其他原因，总是不成功

#include
#include
#include
#include
#include

void delay()
{
int i,j;
for(i=0;i for(j=0;j }
int main()
{
int fd ;
char* string1="AT+CMGF=1\r";
char* string2="AT+CSCS='GSM'\r";
char* string3="AT+CMGS='+8618381306836'\r";
char* string4="Hello\r";
//char* string5="\r";
fd = open("/dev/s3c2410_serial1",O_RDWR);
write(fd,string1,strlen(string1));
delay();
write(fd,string2,strlen(string2));
delay();
write(fd,string3,strlen(string3));
delay();
write(fd,string4,strlen(string4));
delay();
//write(fd,string5,strlen(string5));
// delay();

close(fd);

}