错误的文件描述符 - 简单的UDP客户端

问题描述：

当试图创建一个简单的UDP客户端时，我的代码成功地打开了套接字并从文件中读入一个小缓冲区，以通过命令行发送到由主机地址和端口号指定的服务器参数。错误的文件描述符 - 简单的UDP客户端

但是，sendto和recvfrom都以“坏文件描述符”失败，我找不到原因。

void main(int argc, char* argv[]){ 
int s, n=0, obytes, inbytes; 
struct sockaddr_in sin; 
char *buffer; 
int address = 0; 

//Checks socket 
if((s = socket(AF_INET, SOCK_DGRAM, 0))<0) { 
    printf("Error creating socket\n"); 
    exit(0); 
} 
//Resets values in socket structure 
memset((char*)&sin, 0, sizeof(sin)); 
sin.sin_port = htons(atoi(argv[2])); 
sin.sin_family = AF_INET; 
sin.sin_addr.s_addr = inet_addr(argv[1]); 
printf("%d\n", sin.sin_addr.s_addr); 
/*Opens file to be sent and reads into buffer*/ 
FILE *readFile; 
readFile = fopen(argv[3], "r"); 
//Checks if file to be read can be opened 
if (readFile==NULL) { 
    perror ("Error opening file"); 
} 
//Reads in all the characters to a buffer 
else{ 
    while (!feof(readFile)) { 
     buffer[n] = fgetc (readFile); 
     n++; 
    } 

buffer[n] = '\0'; 
printf ("Total number of bytes: %d\n", n); 
for(int i = 0; i< n; i++){ 
    printf("%c", buffer[i]); 
} 
} 
printf("File was opened\n"); 
//Sends the buffer to the destination designated by the socket structure and checks to see if bytes were sent 
if((obytes = sendto(s, buffer, strlen(buffer), 0, (struct sockaddr *)&sin, sizeof(sin))) == -1) { 
    perror("Sendto() error!"); 
    exit(1); 
} 
printf("%d bytes were sent\n",obytes); 
//Receives response from the server and checks to see if bytes were actually received 
/* if((inbytes = recvfrom(s, buffer, strlen(buffer)+28, 0, (struct sockaddr *)&sin, sizeof(struct sockaddr*))) == -1) { 
    perror("Recvfrom() error!"); 
    exit(1); 
}*/ 
printf("%d bytes were received.\n", inbytes); 
//Closes file 
fclose (readFile); 

}

把你的代码的输出，printf我的意思是。 – 2011-01-30 16:46:39

答

没有输出，这是一种很难，但我注意到的第一件事是，你永远不分配的缓冲区写在文件

答

我看到一些错误/问题：

您从未将n设置为文件的长度
没有内存分配来保存文件
一次读取一个字节的文件将会l条很inefficent
加载你应该知道该文件的长度的文件后，无需使用strlen()
如果是二进制文件，strlen()会失败，因为它会在与第一个嵌入字节停止值0

错误的文件描述符 - 简单的UDP客户端

相关推荐