我用C创建了一个简单的代理服务器代码。它仅在尝试连接到www.yahoo.com/news.html时才有效
但其他网站没有。（例如google或cnn等）
当程序首先进入'accept（）'时，没关系。
所有变量都有自己的值。
但是在'while（）'导致第二个'accept（）'之后，程序关闭了。
直到那时，变量（sockfd2，newsockfd）仍然有自己的价值。
这很奇怪，因为我之前关闭了他们去（）。
我真的不知道为什么我的程序会关闭，为什么它有时会告诉我“地址已经在使用”。
我错过了什么吗？ Plz告诉我。
这是代码。
/*
A simple server in the internet domain using TCP
Usage:./server port (E.g. ./server 10000 )
*/
#include <stdio.h>
#include <sys/types.h> // definitions of a number of data types used in socket.h and netinet/in.h
#include <sys/socket.h> // definitions of structures needed for sockets, e.g. sockaddr
#include <netinet/in.h> // constants and structures needed for internet domain addresses, e.g. sockaddr_in
#include <stdlib.h>
#include <strings.h>
#include <netdb.h> // define structures like hostent
void error(char *msg)
{
perror(msg);
exit(1);
}
char *replaceAll(char *s, const char *olds, const char *news) {
char *result, *sr;
size_t i, count = 0;
size_t oldlen = strlen(olds); if (oldlen < 1) return s;
size_t newlen = strlen(news);
if (newlen != oldlen) {
for (i = 0; s[i] != '\0';) {
if (memcmp(&s[i], olds, oldlen) == 0) count++, i += oldlen;
else i++;
}
} else i = strlen(s);
result = (char *) malloc(i + 1 + count * (newlen - oldlen));
if (result == NULL) return NULL;
sr = result;
while (*s) {
if (memcmp(s, olds, oldlen) == 0) {
memcpy(sr, news, newlen);
sr += newlen;
s += oldlen;
} else *sr++ = *s++;
}
*sr = '\0';
return result;
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd; //descriptors rturn from socket and accept system calls
int sockfd2, newsockfd2; //Socket descriptor
int portno; // port number
int portno2, n2;
socklen_t clilen;
char buffer[1024];
char resMsg[2048];
char bufferForAddr[1024];
char ip[100];
/*sockaddr_in: Structure Containing an Internet Address*/
struct sockaddr_in serv_addr, cli_addr;
struct sockaddr_in serv_addr2;
struct hostent *server2; //contains tons of information, including the server's IP address
struct in_addr **addr_list;
int n;
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
/*Create a new socket
AF_INET: Address Domain is Internet
SOCK_STREAM: Socket Type is STREAM Socket */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
/*browser's port no is 80*/
portno2 = 80;
sockfd2 = socket(AF_INET, SOCK_STREAM, 0); //create a new socket
if (sockfd2 < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]); //atoi converts from String to Integer
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY; //for the server the IP address is always the address that the server is running on
serv_addr.sin_port = htons(portno); //convert from host to network byte order
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) //Bind the socket to the server address
error("ERROR on binding");
listen(sockfd,5); // Listen for socket connections. Backlog queue (connections to wait) is 5
clilen = sizeof(cli_addr);
/*accept function:
1) Block until a new connection is established
2) the new socket descriptor will be used for subsequent communication with the newly connected client.
*/
while(1){
printf("==========================main========================\n");
newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error("ERROR on accept");
bzero(buffer,1024);
n = read(newsockfd,buffer,1023); //Read is a block function. It will read at most 255 bytes
if (n < 0) error("ERROR reading from socket");
printf("Here is the message1: %s\n",buffer);
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/*
get an info about destination site from browser(client)
*/
printf("Here is the message2: %s\n",buffer);
char *reqMSG;
char *address;
reqMSG = replaceAll(buffer, "HTTP/1.1", "HTTP/1.0");
reqMSG = replaceAll(reqMSG, "keep-alive", "close");
//strcat(reqMSG, "\r\nProxy-Connection: keep-alive\r\n");
strcat(reqMSG,"\r\n");
//printf("MSG : %s",reqMSG);
strcpy(bufferForAddr,buffer);
address = strtok(bufferForAddr+11," ");
address = strtok(address,"/");
printf("address : %s\n",address);
printf("MSG : %s\n",reqMSG);
/*
Q2. make a algorithm for filtering about cached site.
*/
/*
if the site is not cached, send the Msg to it's ip address!
in this section, I need to use functions each called connect, write and read.
*/
server2 = gethostbyname(address); //takes a string like "www.yahoo.com", and returns a struct hostent which contains information, as IP address, address type, the length of the addresses...
//get an ip address from hostname
/*
addr_list = (struct in_addr **) server2->h_addr_list;
int i;
for(i = 0; addr_list[i] != NULL; i++)
{
strcpy(ip , inet_ntoa(*addr_list[i]) );
}
*/
if (server2 == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &serv_addr2, sizeof(serv_addr2));
serv_addr2.sin_family = AF_INET; //initialize server's address
bcopy((char *)server2->h_addr, (char *)&serv_addr2.sin_addr.s_addr, server2->h_length);
serv_addr2.sin_port = htons(portno2);
if (connect(sockfd2,(struct sockaddr *)&serv_addr2,sizeof(serv_addr2)) < 0){ //establish a connection to the server
error("ERROR connecting");
}
//send a REQ MSG from above step!
//do{
n2 = write(sockfd2,reqMSG,strlen(reqMSG)); //write to the socket
if (n2 < 0) {
error("ERROR writing to socket");
//break;
}
printf("What's wrong : %s\n",reqMSG);
printf("%s\n",resMsg);
bzero(resMsg,2047);
while (n2 = read(sockfd2,resMsg,2047)>0){ //read from the socket
printf("=================================sub=============================\n");
if (n2 < 0){
error("ERROR reading from socket");
//break;
}
printf("resMsg : %s\n",resMsg);
//printf("\nI'm in the loop!\n");
//}while(1);
/*
if I get response Msg to my destination site, I will return it to my source site.
and wait for closing Msg to browser(client).
*/
write(newsockfd,resMsg,n2); //NOTE: write function returns the number of bytes actually sent out Ñ> this might be less than the number you told it to send
if (n < 0) error("ERROR writing to socket");
bzero(resMsg,2047);
}
close(sockfd2);
/*
make a log file and save this site!
*/
//printf("\nip : %s \n",ip);
close(newsockfd);
}
close(sockfd);
return 0;
}
答案 0 :(得分：0)
befor bind尝试
int tr=1;
if(setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &tr, sizeof(int)) == -1) {
perror("setsockopt");
}