exosip和osip协议栈如何将服务器发送过来的信令信息打印出来，写一个C程序

要使用exosip和osip协议栈来打印服务器发送过来的信令信息，你可以使用以下的C程序代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <exosip2/exosip.h>

int running = 1;

void sigint_handler(int signal) {
    running = 0;
}

int main(int argc, char **argv) {
    osip_message_t *message;
    int status, duration;
    exosip_event_t *evt;
    struct timeval tv;
    exosip_t *ctx;

    signal(SIGINT, sigint_handler);

    ctx = exosip_malloc();
    status = exosip_init(ctx);
    if (status != 0) {
        fprintf(stderr, "Failed to initialize exosip.\n");
        exit(EXIT_FAILURE);
    }

    /* Register with server */
    exosip_listen_address_set(ctx, "udp", "0.0.0.0", 5060, AF_INET6, IPPROTO_UDP, 0);
    exosip_add_authentication_info(ctx, "example.com", "username", "password", NULL, "MD5", NULL);
    exosip_register_build_initial_register(ctx, "sip:example.com", "sip:username@example.com", "sip:example.com", NULL, 3600, &message);
    exosip_register_send_register(ctx, message);

    while (running) {
        tv.tv_sec = 1;
        tv.tv_usec = 0;
        evt = exosip_event_wait(ctx, tv);
        if (evt == NULL) {
            continue;
        }
        switch (evt->type) {
            case EXOSIP_REGISTRATION_FAILURE:
                fprintf(stderr, "Registration failed.\n");
                running = 0;
                break;
            case EXOSIP_REGISTRATION_SUCCESS:
                printf("Registered with server.\n");
                break;
            case EXOSIP_MESSAGE_NEW:
                message = evt->request;
                printf("Received message: %s\n", message->sip);
                break;
            default:
                break;
        }
        exosip_event_free(evt);
    }

    /* Unregister from server */
    exosip_register_build_initial_register(ctx, "sip:example.com", "sip:username@example.com", "sip:example.com", NULL, 0, &message);
    exosip_register_send_register(ctx, message);

    /* Cleanup */
    exosip_quit(ctx);
    exosip_free(ctx);
    osip_free(message);

    return 0;
}

这个程序会使用exosip协议栈来注册到服务器，并且监听服务器发送过来的信令信息。当程序接收到新的信令信息时，它会将信息打印出来。如果你想要修改程序，可以在`case EXOSIP_MESSAGE_NEW`中添加你自己的处理逻辑。