How to write a multithreaded server in C (threads, sockets) 

Thanks. I am a teacher, and producing very good programmers is one of my goals.

Thanks. Glad they're helping.

You're welcome. It sounds like an interesting experiment. I'm not sure from the comment what sort of help you're looking for, but I'd love to hear how things go.

It's definitely not for every application, but it is often indispensable for many subdisciplines like kernels, embedded systems, scientific computing, games and other high-performance systems. It's a tricky language if you're coming from a pure compsci background: for most people C is as close to the silicon as they will ever get., and going any closer usually requires assembly. Coding in C requires a lot of patience and discipline but the payoff in performance, memory footprint and overall control of your processor can be well worth the effort.

@@Kotesu very well said. It's actually too bad your comment was buried in a reply because I think a lot of new programmer's would have an "ah ha" moment reading it.

Yeah, I think so. I'll put event-driven processing and servers (and epoll/kqueue) on my list for future video.

Would be interesting to see some modifications to this server in order to handle them.

Try it out and see. :)

No,it's Visual Studio Code

Exactly my doubt. It doesn't make sense to create a pointer just for storing the client_socket and deleting it in the handle_connection method.

This server should be able to handle multiple clients. It handles each connection in a separate thread, so as long as your connection handling can be done concurrently, then connections shouldn't have to wait.

@@JacobSorber I know but it is my homework

@@lania4334 i have the same homework, could please send it to me , I'll appreciate that.

Meaning that you would like me to prioritize multithreading TCP, or that you want some sort of example where you prioritize different threads managing TCP connections?

@@JacobSorber I want some sort of example that prioritise for different threads with timing signal also managing threads for tcp transmission

Sorry for late reply

Multi Process scheduling with time slice between different process and diffrent priorities to different process

You could use two listening threads, one listening on each port. You could use select (maybe a good topic for a future video). You could also make the sockets nonblocking.

@@JacobSorber We used select , and our project works :)

Glad I could help. Where in Africa?

...where the producer creates the consumers, yes.

It's definitely coming. I've been thinking about this topic, but life's busy, and it might take a little while to show up in video form.

I was, yes.

Probably not. Creating a new process should be more work than creating a new thread.

A thread function only takes one argument (void*). One way to do it would be to create a struct with all the things you want to pass in, and then pass a pointer to that struct.

Jacob Sorber Cool, thank you!

Hi Gadde. I prefer to keep questions here on RU-vid both so they can help more people, but also because I don't always have time to answer them all. If the questions are posted publically, often someone can answer it before I get to it. Of course, I do provide more one-on-one interaction through Patreon.

@@JacobSorber sir actually I want to show u in document sir

@@JacobSorber Develop a basic multithreaded webserver (where multiple threads process multiple client requests simultaneously) with support for different scheduling policies for the client requests....this is the question sir but we have to write in given template

#include "io_helper.h" #include "request.h" #define MAXBUF (8192) // // TODO: add code to create and manage the buffer // // // Sends out HTTP response in case of errors // void request_error(int fd, char *cause, char *errnum, char *shortmsg, char *longmsg) { char buf[MAXBUF], body[MAXBUF]; // Create the body of error message first (have to know its length for header) sprintf(body, "" " " " " " OSTEP WebServer Error " " " " " " %s: %s " " %s: %s " " " " ", errnum, shortmsg, longmsg, cause); // Write out the header information for this response sprintf(buf, "HTTP/1.0 %s %s ", errnum, shortmsg); write_or_die(fd, buf, strlen(buf)); sprintf(buf, "Content-Type: text/html "); write_or_die(fd, buf, strlen(buf)); sprintf(buf, "Content-Length: %lu ", strlen(body)); write_or_die(fd, buf, strlen(buf)); // Write out the body last write_or_die(fd, body, strlen(body)); // close the socket connection close_or_die(fd); } // // Reads and discards everything up to an empty text line // void request_read_headers(int fd) { char buf[MAXBUF]; readline_or_die(fd, buf, MAXBUF); while (strcmp(buf, " ")) { readline_or_die(fd, buf, MAXBUF); } return; } // // Return 1 if static, 0 if dynamic content (executable file) // Calculates filename (and cgiargs, for dynamic) from uri // int request_parse_uri(char *uri, char *filename, char *cgiargs) { char *ptr; if (!strstr(uri, "cgi")) { // static strcpy(cgiargs, ""); sprintf(filename, ".%s", uri); if (uri[strlen(uri)-1] == '/') { strcat(filename, "index.html"); } return 1; } else { // dynamic ptr = index(uri, '?'); if (ptr) { strcpy(cgiargs, ptr+1); *ptr = '\0'; } else { strcpy(cgiargs, ""); } sprintf(filename, ".%s", uri); return 0; } } // // Fills in the filetype given the filename // void request_get_filetype(char *filename, char *filetype) { if (strstr(filename, ".html")) strcpy(filetype, "text/html"); else if (strstr(filename, ".gif")) strcpy(filetype, "image/gif"); else if (strstr(filename, ".jpg")) strcpy(filetype, "image/jpeg"); else strcpy(filetype, "text/plain"); } // // Handles requests for static content // void request_serve_static(int fd, char *filename, int filesize) { int srcfd; char *srcp, filetype[MAXBUF], buf[MAXBUF]; request_get_filetype(filename, filetype); srcfd = open_or_die(filename, O_RDONLY, 0); // Rather than call read() to read the file into memory, // which would require that we allocate a buffer, we memory-map the file srcp = mmap_or_die(0, filesize, PROT_READ, MAP_PRIVATE, srcfd, 0); close_or_die(srcfd); // put together response sprintf(buf, "" "HTTP/1.0 200 OK " "Server: OSTEP WebServer " "Content-Length: %d " "Content-Type: %s ", filesize, filetype); write_or_die(fd, buf, strlen(buf)); // Writes out to the client socket the memory-mapped file write_or_die(fd, srcp, filesize); munmap_or_die(srcp, filesize); } // // Fetches the requests from the buffer and handles them (thread locic) // void* thread_request_serve_static(void* arg) { // TODO: write code to actualy respond to HTTP requests } // // Initial handling of the request // void request_handle(int fd) { int is_static; struct stat sbuf; char buf[MAXBUF], method[MAXBUF], uri[MAXBUF], version[MAXBUF]; char filename[MAXBUF], cgiargs[MAXBUF]; // get the request type, file path and HTTP version readline_or_die(fd, buf, MAXBUF); sscanf(buf, "%s %s %s", method, uri, version); printf("method:%s uri:%s version:%s ", method, uri, version); // verify if the request type is GET is not if (strcasecmp(method, "GET")) { request_error(fd, method, "501", "Not Implemented", "server does not implement this method"); return; } request_read_headers(fd); // check requested content type (static/dynamic) is_static = request_parse_uri(uri, filename, cgiargs); // get some data regarding the requested file, also check if requested file is present on server if (stat(filename, &sbuf) < 0) { request_error(fd, filename, "404", "Not found", "server could not find this file"); return; } // verify if requested content is static if (is_static) { if (!(S_ISREG(sbuf.st_mode)) || !(S_IRUSR & sbuf.st_mode)) { request_error(fd, filename, "403", "Forbidden", "server could not read this file"); return; } // TODO: write code to add HTTP requests in the buffer based on the scheduling policy } else {.. We have to write in this format sir

@@JacobSorber please sir would u solve it it is very urgent sir

int check(int exp, const char *msg) { if (exp == SOCKETERROR) { perror(msg); exit(EXIT_FAILURE); } return exp; }

ok send me a better example