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tcp

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This commit is contained in:
Eggert Jung
2025-12-07 11:55:39 +01:00
parent 9d8640a1c6
commit 385bbc7fb6
1 changed files with 182 additions and 79 deletions
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261
test.c
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@@ -1,96 +1,153 @@
/* -------------------------------------------------------------
* framebuffer_demo.c
* -------------------------------------------------------------
* A tiny example that:
* * allocates a 600×400 RGB‑888 framebuffer in RAM,
* * fills it with a demo pattern,
* * opens an SDL2 window,
* * streams the framebuffer to the window each frame.
* framebuffer_demo_tcp.c
*
* * 600×400 ARGB8888 framebuffer in RAM
* * SDL2 window that displays the framebuffer
* * Simple TCP server (single client) that streams raw pixel data
*
* Build (Linux/macOS):
* gcc -Wall -O2 -std=c11 framebuffer_demo.c -lSDL2 -o framebuffer_demo
* gcc -Wall -Wextra -pedantic -std=c11 framebuffer_demo_tcp.c \
* -lSDL2 -lpthread -o framebuffer_demo_tcp
*
* Run:
* ./framebuffer_demo
* ./framebuffer_demo_tcp # opens a window and listens on 0.0.0.0:12345
*
* Test client (Unix‑like):
* # Send a static colour (red) for one frame
* dd if=/dev/zero bs=1 count=$((600*400*4)) | tr \\0 \\377 > red.bin
* cat red.bin | nc 127.0.0.1 12345
*
* ------------------------------------------------------------- */
#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h> // memcpy, memset
#include <unistd.h> // close, read, write
#include <fcntl.h> // fcntl
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/select.h> // select()
#include <errno.h>
/* -------------------------------------------------------------
* Configuration
* ------------------------------------------------------------- */
#define WIDTH 600
#define HEIGHT 400
#define WIDTH 600
#define HEIGHT 400
#define LISTEN_PORT 12345 // change if you like
#define BACKLOG 1 // only one pending connection
/* -------------------------------------------------------------
* Simple pixel format helpers
* ------------------------------------------------------------- */
/* The framebuffer will be stored as 32‑bit ARGB (0xAARRGGBB). */
typedef Uint32 pixel_t;
typedef Uint32 pixel_t; // 0xAARRGGBB in memory (little‑endian)
/* Build a pixel from separate components (no gamma correction). */
static inline pixel_t make_pixel(Uint8 r, Uint8 g, Uint8 b, Uint8 a) {
/* SDL uses little‑endian, so the order in memory is BGRA.
* Our 0xAARRGGBB layout works fine with SDL_UpdateTexture. */
return (pixel_t)( (a << 24) | (r << 16) | (g << 8) | b );
static inline pixel_t make_pixel(Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
return (pixel_t)((a << 24) | (r << 16) | (g << 8) | b);
}
#define MAKE_OPAQUE_PIXEL(r,g,b) make_pixel((r),(g),(b),0xFF)
/* -------------------------------------------------------------
* Global framebuffer
* Global framebuffer (contiguous block)
* ------------------------------------------------------------- */
static pixel_t framebuffer[HEIGHT][WIDTH];
static pixel_t framebuffer[HEIGHT][WIDTH]; // 600*400*4 = 960 000 bytes
/* -------------------------------------------------------------
* Fill the framebuffer with a demo pattern
* Fill with a cute demo pattern (visible before any network data)
* ------------------------------------------------------------- */
static void init_framebuffer(void)
static void init_demo_pattern(void)
{
for (int y = 0; y < HEIGHT; ++y) {
for (int x = 0; x < WIDTH; ++x) {
/* Example: a smooth red‑to‑green gradient */
Uint8 r = (Uint8)((x * 255) / (WIDTH - 1)); /* left → right */
Uint8 g = (Uint8)((y * 255) / (HEIGHT - 1)); /* top → bottom */
Uint8 b = 0x80; /* constant bluish */
framebuffer[y][x] = make_pixel(r, g, b, 255);
Uint8 r = (Uint8)((x * 255) / (WIDTH - 1));
Uint8 g = (Uint8)((y * 255) / (HEIGHT - 1));
Uint8 b = 0x80;
framebuffer[y][x] = MAKE_OPAQUE_PIXEL(r, g, b);
}
}
}
/* -------------------------------------------------------------
* ---------- TCP SERVER ------------------------------------
* ------------------------------------------------------------- */
/* Returns a non‑blocking listening socket, or -1 on error. */
static int create_listen_socket(void)
{
int lst = socket(AF_INET, SOCK_STREAM, 0);
if (lst < 0) {
perror("socket");
return -1;
}
/* Allow immediate reuse of the address (helps during rapid restarts). */
int opt = 1;
setsockopt(lst, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
struct sockaddr_in addr = {
.sin_family = AF_INET,
.sin_port = htons(LISTEN_PORT),
.sin_addr = { .s_addr = INADDR_ANY }
};
if (bind(lst, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("bind");
close(lst);
return -1;
}
if (listen(lst, BACKLOG) < 0) {
perror("listen");
close(lst);
return -1;
}
/* Make the socket non‑blocking so that accept() never blocks. */
int flags = fcntl(lst, F_GETFL, 0);
fcntl(lst, F_SETFL, flags | O_NONBLOCK);
printf("[net] Listening on 0.0.0.0:%d (single client allowed)\n", LISTEN_PORT);
return lst;
}
/* -------------------------------------------------------------
* Helper: set a socket to non‑blocking mode
* ------------------------------------------------------------- */
static void set_nonblocking(int fd)
{
int flags = fcntl(fd, F_GETFL, 0);
if (flags != -1) fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}
/* -------------------------------------------------------------
* Main entry point
* ------------------------------------------------------------- */
int main(void)
{
/* ---------- SDL initialisation -------------------------------- */
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
fprintf(stderr, "SDL_Init error: %s\n", SDL_GetError());
return EXIT_FAILURE;
}
/* ---------------------------------------------------------
* Create a window and a renderer (software accelerated is fine)
* --------------------------------------------------------- */
SDL_Window *window = SDL_CreateWindow(
"Framebuffer Demo",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
WIDTH,
HEIGHT,
SDL_WINDOW_SHOWN
);
SDL_Window *window = SDL_CreateWindow("Framebuffer Demo – TCP Input",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
WIDTH, HEIGHT,
SDL_WINDOW_SHOWN);
if (!window) {
fprintf(stderr, "SDL_CreateWindow error: %s\n", SDL_GetError());
SDL_Quit();
return EXIT_FAILURE;
}
SDL_Renderer *renderer = SDL_CreateRenderer(
window,
-1,
SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC
);
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1,
SDL_RENDERER_ACCELERATED |
SDL_RENDERER_PRESENTVSYNC);
if (!renderer) {
fprintf(stderr, "SDL_CreateRenderer error: %s\n", SDL_GetError());
SDL_DestroyWindow(window);
@@ -98,17 +155,10 @@ int main(void)
return EXIT_FAILURE;
}
/* ---------------------------------------------------------
* Create a texture that will hold the framebuffer.
* SDL_PIXELFORMAT_ARGB8888 matches our pixel_t layout.
* --------------------------------------------------------- */
SDL_Texture *texture = SDL_CreateTexture(
renderer,
SDL_PIXELFORMAT_ARGB8888,
SDL_TEXTUREACCESS_STREAMING,
WIDTH,
HEIGHT
);
SDL_Texture *texture = SDL_CreateTexture(renderer,
SDL_PIXELFORMAT_ARGB8888,
SDL_TEXTUREACCESS_STREAMING,
WIDTH, HEIGHT);
if (!texture) {
fprintf(stderr, "SDL_CreateTexture error: %s\n", SDL_GetError());
SDL_DestroyRenderer(renderer);
@@ -117,57 +167,109 @@ int main(void)
return EXIT_FAILURE;
}
/* ---------------------------------------------------------
* Initialise the framebuffer with example data.
* --------------------------------------------------------- */
init_framebuffer();
/* ---------- Initialise demo framebuffer ----------------------- */
init_demo_pattern();
/* ---------- Initialise networking ----------------------------- */
int listen_sock = create_listen_socket();
if (listen_sock < 0) {
/* Continue without network – the window will just show the demo. */
fprintf(stderr, "[net] Continuing without network input.\n");
}
int client_sock = -1; // -1 means “no client connected”
size_t bytes_needed = WIDTH * HEIGHT * sizeof(pixel_t);
size_t recv_offset = 0; // how many bytes of the current frame we already have
/* ---------------------------------------------------------
* Main loop
* --------------------------------------------------------- */
bool quit = false;
SDL_Event ev;
/* ---------- Main loop ---------------------------------------- */
while (!quit) {
/* ----- Event handling --------------------------------- */
/* ---- 1) Process SDL events (non‑blocking) ------------- */
while (SDL_PollEvent(&ev)) {
if (ev.type == SDL_QUIT) {
if (ev.type == SDL_QUIT) quit = true;
else if (ev.type == SDL_KEYDOWN && ev.key.keysym.sym == SDLK_ESCAPE)
quit = true;
} else if (ev.type == SDL_KEYDOWN) {
/* Press Escape to quit */
if (ev.key.keysym.sym == SDLK_ESCAPE)
quit = true;
}
/* ---- 2) Accept a client if we have none yet ------------- */
if (listen_sock >= 0 && client_sock < 0) {
struct sockaddr_in remote;
socklen_t remote_len = sizeof(remote);
int tmp = accept(listen_sock,
(struct sockaddr *)&remote,
&remote_len);
if (tmp >= 0) {
client_sock = tmp;
set_nonblocking(client_sock);
recv_offset = 0; // start a fresh frame
char ip[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &remote.sin_addr, ip, sizeof(ip));
printf("[net] Client connected from %s:%d\n", ip, ntohs(remote.sin_port));
} else if (errno != EAGAIN && errno != EWOULDBLOCK) {
perror("[net] accept");
}
}
/* ----- Update texture from the framebuffer ------------ */
/* ---- 3) Read raw pixel data from the client ------------- */
if (client_sock >= 0) {
/* Try to read the remainder of the current frame. */
size_t still_needed = bytes_needed - recv_offset;
ssize_t n = recv(client_sock,
((Uint8 *)framebuffer) + recv_offset,
still_needed,
0);
if (n > 0) {
recv_offset += (size_t)n;
if (recv_offset == bytes_needed) {
/* Full frame received – it will be displayed on the next render pass. */
recv_offset = 0; // start collecting the next frame
}
} else if (n == 0) {
/* Client performed an orderly shutdown. */
printf("[net] Client disconnected.\n");
close(client_sock);
client_sock = -1;
} else if (n < 0) {
if (errno != EAGAIN && errno != EWOULDBLOCK) {
perror("[net] recv");
close(client_sock);
client_sock = -1;
}
/* If EAGAIN/EWOULDBLOCK we simply have no more data right now. */
}
}
/* ---- 4) Copy framebuffer into texture ------------------- */
void *tex_pixels;
int tex_pitch; // bytes per row
int tex_pitch;
if (SDL_LockTexture(texture, NULL, &tex_pixels, &tex_pitch) != 0) {
fprintf(stderr, "SDL_LockTexture error: %s\n", SDL_GetError());
break;
}
/* Copy line‑by‑line because the pitch may differ from WIDTH*4 */
/* The texture pitch may be larger than WIDTH*4, so copy line‑by‑line. */
for (int y = 0; y < HEIGHT; ++y) {
memcpy(
(Uint8 *)tex_pixels + y * tex_pitch,
framebuffer[y],
WIDTH * sizeof(pixel_t)
);
memcpy((Uint8 *)tex_pixels + y * tex_pitch,
framebuffer[y],
WIDTH * sizeof(pixel_t));
}
SDL_UnlockTexture(texture);
/* ----- Render ------------------------------------------ */
/* ---- 5) Render ------------------------------------------ */
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderPresent(renderer);
/* The loop runs at the monitor refresh rate thanks to VSYNC. */
/* VSYNC in the renderer caps the loop to the monitor refresh rate. */
}
/* ---------------------------------------------------------
/* -------------------------------------------------------------
* Cleanup
* --------------------------------------------------------- */
* ------------------------------------------------------------- */
if (client_sock >= 0) close(client_sock);
if (listen_sock >= 0) close(listen_sock);
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
@@ -175,3 +277,4 @@ int main(void)
return EXIT_SUCCESS;
}