Here there are some useful functions
Click to expand!
struct sockaddr_in remote;
printf("Client ip: %d.%d.%d.%d \nPort: %d",
*((unsigned char*) &remote.sin_addr.s_addr),
*((unsigned char*) &remote.sin_addr.s_addr+1),
*((unsigned char*) &remote.sin_addr.s_addr+2),
*((unsigned char*) &remote.sin_addr.s_addr+3),
ntohs(remote.sin_port)
);Click to expand!
/**
struct hostent {
char *h_name; // official name of host
char **h_aliases; // alias list
int h_addrtype; // host address type
int h_length; // length of address
char **h_addr_list; // list of addresses
}
#define h_addr h_addr_list[0] // for backward compatibility
*/
char hostname[1000];
sprintf(hostname, "www.example.com");
struct hostent *remoteIp;
remoteIp = gethostbyname(hostname);
printf("Indirizzo di %s : %d.%d.%d.%d\n", hostname,
(unsigned char)(remoteIp->h_addr[0]), (unsigned char)(remoteIp->h_addr[1]),
(unsigned char)(remoteIp->h_addr[2]), (unsigned char)(remoteIp->h_addr[3]));An example of HTTP Date
- Thu, 17 Oct 2019 07:18:26 GMT
So HTTP date format is
- %a, %d %b %Y %H:%M:%S %Z
Here are some functions for handling HTTP Dates:
Click to expand!
char date_buf[1000];
char* getNowHttpDate(){
char* format = "%a, %d %b %Y %H:%M:%S %Z";
time_t now = time(0);
struct tm tm = *gmtime(&now);
strftime(date_buf, sizeof(date_buf), format, &tm);
printf("Time is: [%s]\n", date_buf);
return date_buf;
}Click to expand!
void saveEpoch() {
FILE* cached = fopen(cacheName, "w+");
if (cached != NULL) {
time_t epochNow = time(NULL);
fprintf(cached, "%lu\n", (unsigned long)epochNow);
}
fclose(cached);
}Click to expand!
time_t httpDateToEpoch(char * lastModified) {
char* format = "%a, %d %b %Y %H:%M:%S %Z";
struct tm* httpTime = malloc(sizeof(struct tm));
strptime(lastModified, format, httpTime); // man 3 strptime
time_t epochRemote = mktime(httpTime); // convert tm to epoch
return epochRemote;
}Click to expand!
/**
* Replace char '/' with '_' in the given string
*/
void charReplace(char* s) {
for (int i=0; s[i]; i++)
if (s[i] == '/')
s[i] = '_';
}
unsigned char expired(char * uri, char * last_modified){
char resourceName[] = "/";
// Replace '/' with '_' in resourceName
char tmp[100];
strcpy(tmp, resourceName);
charReplace(tmp);
// Save cacheName
char cacheName[1000];
strcpy(cacheName, "./cache/");
strcat(cacheName, tmp);
// Open cacheName file
FILE * cached = fopen(cacheName, "r");
if (cached == NULL)
return 1;
// read first line of cached file
char * line = 0; size_t len = 0;
getline(&line, &len, cached);
if (httpDateToEpoch(last_modified) < httpDateToEpoch(line))
return 0;
return 1;
}Click to expand!
FILE *fin;
fin = fopen(uri + 1, "rt"));
if (fin == NULL) {
sprintf(response, "HTTP/1.1 404 File not found\r\n\r\n<html>File non trovato</html>");
t = write(s2, response, strlen(response));
if (t == -1) {
perror("write fallita"); return -1;
}
} else {
content_length = 0;
while ((c = fgetc(fin)) != EOF) content_length++; // get file length
sprintf(response, "HTTP/1.1 200 OK\r\nConnection: keep-alive\r\nContent-Length: %d\r\n\r\n", content_length);
printf("Response: %s\n", response);
//send headers
t = write(s2, response, strlen(response));
if (t==-1) {
perror("write fallita"); return -1;
}
rewind(fin); // move pointer to the begin of the file
//re-read and send the file, char per char
while ((c = fgetc(fin)) != EOF) {
if (write(s2, (unsigned char *)&c, 1) != 1)
perror("Write fallita");
}
fclose(fin);
}Useful info
/etc/services: To know all the TCP ports available at the application level.
/etc/protocols. Know assigned Internet Protocol Numbers. In the IPv4 there is an 8 bit field "Protocol" to identify the next level protocol.In IPv6 this field is called the "Next Header" field.
nslookup : finds the ip address of the specified URL (example: www.google.com)
netstat -rn shows routing table
traceroute routes an ip packet in which path it travels by printing the IP of every gateway that decides to drop the packet that was forged with low TTL (time to live, decremented on every hop) count.
curl is a command-line tool to transfer data from or to a server, using one of the supported protocols (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP)
$ curl http://example.com/
$ curl -v http://example.com/
$ curl -v http://example.com/ --headers [OR -H] "HeaderName: HeaderValue"
Send Curl request using Basic Authentication, --basic is the default authentication mechanism so no need to specify it
$ curl -v http://example.com/ -u "username:password"
$ curl -v http://example.com/ --proxy [OR -x] http://SERVER:PORT
Copy the .vimrc file into your home directory on the server using Unix's scp command.
Remember to change MATRICOLA with your Unipd Student ID.
Login using your SSH credentials.
scp -O ./.vimrc MATRICOLA@SERVER_IP:/home/MATRICOLA/.vimrc
This .vimrc config file allows you to:
- Use your mouse: scrolling wheel to move up or down, click and point
- Move line Up/Down using Ctrl+Shift+Up/Down
- Press F8 to Compile the C program without exiting Vim
- Press F9 to Execute the C program without exiting Vim
- Auto close brackets
- Replace tabs with 3 spaces
- Highlight matching parentheses
- Auto indent on brackets
- Show line number
- Highlight current line
- Search characters as they are entered
- Search is case insesitive if no case letters are entered, but case sensitive if case letters are entered
- Highlight search results
Click to expand!
Search is UNIDIRECTIONAL but when the search reach one end of the file, pressing n continues the search, starting from the other end of the file.
To search forward use /
To search bacward use ?
x es:
ESC (go into Command mode)
/query (forward)
?query (backward)
ENTER (to stop writing in the search query)
(now all search results of the query are highlighted)
n (to move to the NEXT occurence in the search results)
N (to move to the PREVIOUS occurence in the search results)
ESC (to exit Search mode)
Click to expand!
To Compile press F8
To Execute press F9
ESC (go into Command mode)
F8 (compile shortcut)
F9 (execute shortcut)
CTRL+C (to exit compilation/executable)
Enter (to re-enter in vim)
Click to expand!
ESC (go into Command mode)
CTRL+SHIFT+PAGE UP (to move line up)
CTRL+SHIFT+PAGE DOWN (to move line down)
i (go into Insert mode)
Click to expand!
Select with the mouse the text you want to copy
[ALTERNATIVE
ESC (go into Command mode)
V100G (to select from current line to line 100, included, using Visual mode)]
y (to Copy/yank)
d (to Cut/delete)
p (to Paste after the cursor)
Click to expand!
Open the file from which you want to copy in Vim using:
vi ogFile.c (ogFile is the destination file)
ESC (go into Command mode)
:ePATH/file (open 'source' file at Path)
(select the lines that you want to copy)
y (copy/yank)
:q (close the 'source' file)
vi ogFile.c (open the 'destination' file)
p (paste the copied lines into the 'destination' file)
Click to expand!
ESC (go into Command mode)
u (to Undo)
Click to expand!
CTRL + s (now screen is frozen)
(every command that you type when the screen is frozen will be executed, it just won't be displayed in the terminal)
CTRL + q (to unfreeze the screen)