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uppercase.c

/** sudo apt-get install libevent-dev  # libevent-devel for yum* Server:* cc -g uppercase.c -levent* ./a.out* Client:* $ ncat 192.168.0.107 9995* hello, world* HELLO, WORLD*/
#include <stdlib.h> /* free */
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
#include <signal.h>
#ifndef _WIN32
#include <netinet/in.h>
# ifdef _XOPEN_SOURCE_EXTENDED
#  include <arpa/inet.h>
# endif
#include <sys/socket.h>
#endif#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <event2/listener.h>
#include <event2/util.h>
#include <event2/event.h>#define PORT 9995
#define BUFFER_SIZE 1024static void listener_cb(struct evconnlistener *, evutil_socket_t,struct sockaddr *, int socklen, void *);
static void conn_readcb(struct bufferevent *, void *);
static void conn_eventcb(struct bufferevent *, short, void *);
static void signal_cb(evutil_socket_t, short, void *);int main(int argc, char **argv) {struct event_base *base;struct evconnlistener *listener;struct event *signal_event;struct sockaddr_in sin = {0};#ifdef _WIN32WSADATA wsa_data;WSAStartup(0x0201, &wsa_data);
#endifbase = event_base_new();if (!base) {fprintf(stderr, "Could not initialize libevent!\n");return 1;}sin.sin_family = AF_INET;sin.sin_port = htons(PORT);listener = evconnlistener_new_bind(base, listener_cb, (void *)base,LEV_OPT_REUSEABLE | LEV_OPT_CLOSE_ON_FREE, -1,(struct sockaddr*)&sin,sizeof(sin));if (!listener) {fprintf(stderr, "Could not create a listener!\n");return 1;}signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);if (!signal_event || event_add(signal_event, NULL) < 0) {fprintf(stderr, "Could not create/add a signal event!\n");return 1;}event_base_dispatch(base);evconnlistener_free(listener);event_free(signal_event);event_base_free(base);printf("Server shut down.\n");return 0;
}static void listener_cb(struct evconnlistener *listener, evutil_socket_t fd,struct sockaddr *sa, int socklen, void *user_data) {struct event_base *base = user_data;struct bufferevent *bev;bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);if (!bev) {fprintf(stderr, "Error constructing bufferevent!\n");event_base_loopbreak(base);return;}bufferevent_setcb(bev, conn_readcb, NULL, conn_eventcb, NULL);bufferevent_enable(bev, EV_READ | EV_WRITE);
}static void conn_readcb(struct bufferevent *bev, void *user_data) {struct evbuffer *input = bufferevent_get_input(bev);struct evbuffer *output = bufferevent_get_output(bev);char *line;size_t n, i;while ((line = evbuffer_readln(input, &n, EVBUFFER_EOL_LF)) != NULL) {if (strncmp(line, "exit", 4)==0 || (strncmp(line, "quit", 4)==0)) {free(line);bufferevent_free(bev);return;}for (i = 0; i < n; i++) {line[i] = toupper((unsigned char)line[i]);}evbuffer_add(output, line, n);evbuffer_add(output, "\n", 1);  /* Add newline for proper response */free(line);}
}static void conn_eventcb(struct bufferevent *bev, short events, void *user_data) {if (events & BEV_EVENT_EOF) {printf("Connection closed.\n");} else if (events & BEV_EVENT_ERROR) {printf("Got an error on the connection: %s\n", strerror(errno));}bufferevent_free(bev);
}static void signal_cb(evutil_socket_t sig, short events, void *user_data) {struct event_base *base = user_data;struct timeval delay = { 0, 10 };printf("Caught an interrupt signal; exiting cleanly in 10ms.\n");event_base_loopexit(base, &delay);
}

mzh@raspberrypi:~/workspace $ cc -g uppercase.c -levent
mzh@raspberrypi:~/workspace $ ./a.out 
 

mzh@DESKTOP-GITL67P MINGW64 ~
$ ncat 192.168.0.107 9995
libnsock ssl_init_helper(): OpenSSL legacy provider failed to load.

hello,world
HELLO,WORLD
zjrcu96592
ZJRCU96592
quit

Ncat: ▒▒▒▒▒▒▒▒е▒▒▒▒▒▒ֹ▒▒һ▒▒▒ѽ▒▒▒▒▒▒▒▒ӡ▒ .
 

static void conn_readcb(struct bufferevent *bev, void *user_data) {
    server_context_t *server_ctx = (server_context_t *)user_data;
    struct evbuffer *input = bufferevent_get_input(bev);
    struct evbuffer *output = bufferevent_get_output(bev);
    char buffer[BUFFER_SIZE];
    int n;

    while ((n = evbuffer_remove(input, buffer, sizeof(buffer))) > 0) {
        for (int i = 0; i < n; i++) {
            buffer[i] = toupper((unsigned char)buffer[i]);
        }
        evbuffer_add(output, buffer, n);
    }
}