linux下网络编程 端口设置的问题

#include "csapp.h"

#define MAX_ARG_NUM 10
#define MAXLINE    512

#define PEER_PORT  1719

struct Udp2SipMsg
{
  int argc;

  char *argv[MAX_ARG_NUM];
  char buf[MAXLINE];
} udp2sipmsg;

char *sendbuf;
char *recvbuf;

struct sockaddr_in host,peer;
struct hostent    *peerp;
char  *peername;

int sockfd=0;

int
udp_init(void/*char *peername*/)
{
  sendbuf=(char *)malloc(sizeof(udp2sipmsg.buf[MAXLINE]));
  recvbuf=(char *)malloc(sizeof(udp2sipmsg.buf[MAXLINE]));

  bzero(sendbuf,sizeof(udp2sipmsg.buf[MAXLINE]));
  bzero(recvbuf,sizeof(udp2sipmsg.buf[MAXLINE]));
 

  sockfd=socket(AF_INET,SOCK_DGRAM,0);
  if(sockfd <=0)
    perror("socket error");
  printf("sockfd=%d",sockfd);
   
  int optval = 1;

    setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char *)&optval, sizeof(optval));
 

  char *peername="heyunping";
  if((peerp=gethostbyname(peername))==NULL)
      perror("getpeerbyname error");