我是套接字编程的新手,我正在尝试了解htons()
. 我已经在互联网上阅读了一些类似this和this的教程。但我不明白到底htons()
是什么。我尝试了以下代码:
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int main( int argc, char *argv[] )
{
int sockfd, newsockfd, portno, clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
/* First call to socket() function */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
{
perror("ERROR opening socket");
exit(1);
}
/* Initialize socket structure */
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = 5001;
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
/* Now bind the host address using bind() call.*/
if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0)
{
perror("ERROR on binding");
exit(1);
}
/* Now start listening for the clients, here process will
* go in sleep mode and will wait for the incoming connection
*/
listen(sockfd,5);
clilen = sizeof(cli_addr);
/* Accept actual connection from the client */
newsockfd = accept(sockfd, (struct sockaddr *)&cli_addr,
&clilen);
if (newsockfd < 0)
{
perror("ERROR on accept");
exit(1);
}
/* If connection is established then start communicating */
bzero(buffer,256);
n = read( newsockfd,buffer,255 );
if (n < 0)
{
perror("ERROR reading from socket");
exit(1);
}
printf("Here is the message: %s\n",buffer);
/* Write a response to the client */
n = write(newsockfd,"I got your message",18);
if (n < 0)
{
perror("ERROR writing to socket");
exit(1);
}
return 0;
}
的值sin_port
显示为35091
在调试时,我不明白如何portno
从 更改5001
为35091
。有人可以解释一下价值变化的原因吗?