Use const pointers when possible

Sending data only require to read the input buffer, so declare it const.

app/src/net.c

@@ -82,11 +82,11 @@ ssize_t net_recv_all(socket_t socket, void *buf, size_t len) {
     return recv(socket, buf, len, MSG_WAITALL);
 }
 
-ssize_t net_send(socket_t socket, void *buf, size_t len) {
+ssize_t net_send(socket_t socket, const void *buf, size_t len) {
     return send(socket, buf, len, 0);
 }
 
-ssize_t net_send_all(socket_t socket, void *buf, size_t len) {
+ssize_t net_send_all(socket_t socket, const void *buf, size_t len) {
     ssize_t w;
     while (len > 0) {
         w = send(socket, buf, len, 0);

app/src/net.h

@@ -26,8 +26,8 @@ socket_t net_accept(socket_t server_socket);
 // the _all versions wait/retry until len bytes have been written/read
 ssize_t net_recv(socket_t socket, void *buf, size_t len);
 ssize_t net_recv_all(socket_t socket, void *buf, size_t len);
-ssize_t net_send(socket_t socket, void *buf, size_t len);
-ssize_t net_send_all(socket_t socket, void *buf, size_t len);
+ssize_t net_send(socket_t socket, const void *buf, size_t len);
+ssize_t net_send_all(socket_t socket, const void *buf, size_t len);
 // how is SHUT_RD (read), SHUT_WR (write) or SHUT_RDWR (both)
 SDL_bool net_shutdown(socket_t socket, int how);
 SDL_bool net_close(socket_t socket);