I want to console every time I receive it on a UDP socket.

#include<stdio.h>
# include <string.h>
# include "udp_socket.hpp"
# include <unistd.h>

constint PortNumber = 50000; // 49152 through 65535
const char*IPaddress="172.0.0.1"; // recv side ip

const int recv_max_size = 10;
const int64_t timeout_setting=10;

int main(intargc, char**argv){
    UDPSocket udp0 (IPaddress, PortNumber);

    udp0.udp_bind();

    for(inti=0;i<recv_max_size;i++){
        if(udp0.timeout(timeout_setting)==0){
            error("time out";
            break;
        }
        std::string data=udp0.udp_recv();
        printf("%s\n", data.c_str());
    }

    return 0;
}

#include<sys/types.h>
# include<sys/socket.h>
# include <netinet/in.h>
# include <arpa/inet.h>
# include <unistd.h>
# include <string>
# include <string.h>

class UDPSocket {
    intsock;
    structure sockaddr_inaddr;
public:
    UDPSocket (std::string address, int port) {
        sock=socket(AF_INET, SOCK_DGRAM, 0);
        addr.sin_family=AF_INET;
        addr.sin_addr.s_addr=inet_addr(address.c_str());
        addr.sin_port = htons(port);
    }
    void udp_send(std::string word) {
        sendto(sock, word.c_str(), word.length(), 0, (struct sockaddr*)&addr,sizeof(addr));
    }

    void udp_bind(){
        bind(sock,(construct sockaddr*)&addr,sizeof(addr)));
    }

    int timeout(int64_tsec){
        FD_ZERO(&readfds);
        FD_SET(sd, & readfds);
        tv.tv_sec=sec;
        return select(sd+1,&readfds,NULL,NULL,&tv);
    }

    std::string udp_recv(){
        #define BUFFER_MAX400
        char buf [BUFFER_MAX];
        memset(buf,0,sizeof(buf));
        recv(sock, buf, sizeof(buf), 0);
        return std:string(buf);
    }
    void udp_recv(char*buf, int size){
        memset(buf,0,size);
        recv(sock, buf, size, 0);
    }

    ~UDPSocket(){
        close(sock);
    }
private:
    intsd;
    structure sockaddr_inaddr;
    socklen_tsin_size;
    structure sockaddr_in from_addr;
    fd_set readfds;
    structure timeval tv;
};

11:38:10.804218 select (9,[8], NULL, NULL, {tv_sec=140262861, tv_usec=519539})=1 (in[8], left {tv_sec=140262859, tv_usec=184927})<2.334631>
11:38:13.139160 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")}, [32657->16] = 11<0.000007>
11:38:13.139263fstat(1,{st_mode=S_IFIFO|0600,st_size=0,...}) = 0<0.000009>
11:38:13.139312 select (9, [8], NULL, NULL, {tv_sec=5, tv_usec=184927}) = 1 (in [8], left {tv_sec=4, tv_usec=682655}) <0.502286>
11:38:13.641707 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000011>
11:38:13.641792 select(9,[8], NULL, NULL, {tv_sec=5, tv_usec=682655})=1(in[8], left {tv_sec=4, tv_usec=745982})<0.936685>
11:38:14.578538 recvfrom(8, "hello wold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000007>
11:38:14.578597 select (9, [8], NULL, NULL, {tv_sec=5, tv_usec=745982}) = 1 (in [8], left {tv_sec=5, tv_usec=478603}) <0.267391>
11:38:14.846041 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000007>
11:38:14.846098 select (9, [8], NULL, NULL, {tv_sec=5, tv_usec=478603}) = 1 (in [8], left {tv_sec=5, tv_usec=278146}) <0.200496>
11:38:15.046662 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000008>
11:38:15.046730 select (9,[8], NULL, NULL, {tv_sec=5, tv_usec=278146}) = 1 (in[8], left {tv_sec=2, tv_usec=754525}) <2.523639>
11:38:17.570431 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000011>
11:38:17.570497 select (9,[8], NULL, NULL, {tv_sec=5, tv_usec=754525}) = 1 (in[8], left {tv_sec=4, tv_usec=82849}) <1.671736>
11:38:19.242312 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000008>
11:38:19.242372 select (9,[8], NULL, NULL, {tv_sec=5, tv_usec=82849}) = 1 (in[8], left {tv_sec=3, tv_usec=527405}) <1.555459>
11:38:20.797890 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000008>
11:38:20.797968 select(9,[8], NULL, NULL, {tv_sec=5, tv_usec=527405})=1(in[8], left {tv_sec=3, tv_usec=153375})<2.374050>
11:38:23.172093 recvfrom (8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000010>
11:38:23.172182 select (9,[8], NULL, NULL, {tv_sec=5, tv_usec=153375}) = 1 (in[8], left {tv_sec=2, tv_usec=996190}) <2.157256>
11:38:25.329508 recvfrom(8, "hellowold", 1500, 0, {sa_family=AF_INET, sin_port=htons(51618), sin_addr=inet_addr("127.0.0.1")} ,[16]) = 11<0.000008>
11:38:25.329580 close(8) = 0<0.000016>
11:38:25.329626 write (1, "hellowold\nhellowold\nhellowo" ..., 120) = 120<0.000012>
11:38:25.329682 exit_group(0)=?
11:38:25.329806++++exited with 0++++