client.h

#ifndef _HY_TCP_H
#define _HY_TCP_H

typedef void (* recv_callback)(char *data, int len);//定義回撥
typedef struct param{
        recv_callback callback;
    } callback_param;

int tcp_dns_change(char *dns, char *str, int size);
int tcp_connect(char *IP,int PORT);
void tcp_disconnect(void);
int tcp_send(char
 
 *buf);
int tcp_recv(char *buf, int size);
void *thread_recv(void *param);
void tcp_register_callback(recv_callback cb); //呼叫回撥函式


#endif

client.c

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <sys/types.h>
#include <netinet/in
 
.h>
#include <arpa/inet.h>
#include <string.h>
#include <netdb.h>
#include <syslog.h>
#include <pthread.h>
#include <poll.h>
#include "hy_tcp.h"

int sockfd;

enum {
    STATE_NOCONNECTED,  //未連線
    STATE_CONNECTED,    //已連線
    STATE_DISCONNECTE   //連線斷開
};

int connect_state = STATE_NOCONNECTED;

 
int tcp_dns_change(char *dns, char *str, int size)
{
    struct hostent *hptr;
    hptr = gethostbyname(dns);
    if (hptr == NULL) {
        syslog(LOG_ERR, "gethostbyname error");
        return -1;
    }
    syslog(LOG_INFO, "ipaddr:%s\n", inet_ntop(hptr->h_addrtype, hptr->h_addr, str, size));
    return 0;
}

int tcp_connect(char *IP,int PORT)
{
    if (connect_state == STATE_NOCONNECTED) {
        struct sockaddr_in server_addr;
        sockfd = socket(AF_INET, SOCK_STREAM, 0);
        if (sockfd < 0) {
            syslog(LOG_ERR, "create socket failed!\n");
            return -1;
        }
        memset(&server_addr, 0, sizeof(server_addr));
        server_addr.sin_family = AF_INET;
        server_addr.sin_port = htons(PORT);
        server_addr.sin_addr.s_addr = inet_addr(IP);
        if (connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
            syslog(LOG_ERR, "connet error!\n");
            return -1;
        }
        connect_state = STATE_CONNECTED;
        syslog(LOG_INFO, "connect success!\n");
        return 0;
    }
    else
        return -1;
}

void tcp_disconnect(void)
{
    if (connect_state != STATE_NOCONNECTED) {
        close(sockfd);
        syslog(LOG_INFO, "connect is break!\n");
    }
}

int tcp_send(char *buf)
{
    if (connect_state == STATE_CONNECTED) {
        return send(sockfd, buf, strlen(buf)+1, 0);
    }
    else
        return -1;
}

void *thread_recv(void *param)
{
    int ret;
    static char buf[2048] = {0};
    char heartbeat_buf[] = "heartbeat data";
    callback_param *p = (callback_param *)param;
    struct pollfd c_poll;
    c_poll.fd = sockfd;
    c_poll.events = POLLIN;
    memset(buf, 0, sizeof(buf));
    while (1) {

        if (connect_state == STATE_CONNECTED) {
            ret = poll(&c_poll, 1, 5000);
            if (ret < 0) {
                syslog(LOG_ERR, "poll error!\n");
                break;
            }
            else if (0 == ret) {
                if (send(sockfd, heartbeat_buf, sizeof(heartbeat_buf), 0) < 0) {
                    connect_state = STATE_DISCONNECTE;
                    syslog(LOG_ERR, "disconnect!\n");
                    break;
                }
            }
            else {
                if (recv(sockfd, buf, sizeof(buf), 0) > 0) {
                    syslog(LOG_INFO, "recv:%s\n", buf);
                    p->callback(buf, sizeof(buf));
                }
            }
        }
        else
            break;
    }
}

void tcp_register_callback(recv_callback cb)
{
    pthread_t recv_t;
    static callback_param param;
    param.callback = cb;
    pthread_create(&recv_t, NULL, thread_recv, (void *)&param);
    pthread_detach(recv_t);
}

main.c

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#include "hy_tcp.h"
#include "hy_udp.h"

#define PORT 6000   //伺服器埠號
#if 1

void r_callback(char *msg, int len) {
    
}

int main(int argc, char *argv[])
{
    char recv_buf[1024] = {0};
    char send_buf[1024] = {0};
    char str[16];
    recv_callback func = r_callback;
    if(argc < 2){
        printf("required parameter missing\n");
        return -1;
    }
    //tcp_dns_change(argv[1], str, sizeof(str));
    tcp_connect(argv[1],PORT);
    tcp_register_callback(func);
    
    while(1){
        memset(send_buf,0,sizeof(send_buf));
        printf("please input something\n");
        scanf("%s",send_buf);
        tcp_send(send_buf);
    }
    tcp_disconnect();
    return 0;
}
#endif