//前面是正常UDP client架構
int sfd = 0;
sfd = open(argv[2], O_RDONLY);    //argv[2]是執行程式時輸入的檔名
struct stat sb;
stat(argv[2], &sb);
long long int filesize = (long long int)sb.st_size;
long int cal = filesize/1024 + 1;
int n = 0;

char buf[1024];

for(long int i = 0; i < cal; i++)
{
    n = read(sfd, buf, 1024);
    //n的確會是1024，但strlen(buf)卻不到1024

    //下面是傳檔處理，就不列了
}

Line 3: warning: data definition has no type or storage class
Line 3: error: redefinition of 'sfd'
Line 2: error: previous definition of 'sfd' was here
Line 3: error: 'argv' undeclared here (not in a function)
Line 3: error: 'O_RDONLY' undeclared here (not in a function)
Line 3: error: initializer element is not constant
Line 5: error: expected ')' before '[' token
Line 6: error: invalid use of undefined type 'struct stat'
Line 7: error: initializer element is not constant
Line 12: error: expected identifier or '(' before 'for'
Line 12: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
Line 12: error: expected '=', ',', ';', 'asm' or '__attribute__' before '++' token