我正在尝试为Telnet客户端服务器 session 编写代码，以在它们之间发送协商。就像会，不会，不会，不会。我使用套接字编程编写了一个基本的客户机-服务器程序。
如果我能通过协商将如何将客户端/服务器修改为telnet客户端服务器，那将有很大的帮助。以下是代码:
在这里输入代码
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netdb.h>
char buf1[] = {0xff, 0xfb, 0x18, 0xff, 0xfb, 0x1f};
char buf2[] = {0xff, 0xfc, 0x20, 0xff, 0xfc, 0x23, 0xff, 0xfb, 0x27};
char buf3[] = {0xff, 0xfa, 0x1f, 0x00, 0x78, 0x00, 0x32, 0xff, 0xf0};
char buf4[] = {0xff, 0xfa, 0x27, 0x00, 0xff, 0xf0, 0xff, 0xfa, 0x18, 0x00, 0x41, 0x4e, 0x53, 0x49, 0xff, 0xf0};
char buf5[] = {0xff, 0xfd, 0x03};
char buf6[] = {0xff, 0xfb, 0x01, 0xff, 0xfe, 0x05, 0xff, 0xfc, 0x21};
char buf7[] = {0xff, 0xfc, 0x01};
char buf8[] = {0xff, 0xfd, 0x01};
void read (int sock)
{
char buffer[256];
/* Now read server response */
memset(buffer, 0, sizeof(buffer));
int n = recv( sock, buffer, 255, 0 );
if (n < 0)
{
perror("ERROR reading from socket");
return;
}
printf("%d bytes received buffer is: %s\n", n, buffer);
for (int i = 0; i < n; i++)
printf("%2x ", buffer[i]);
printf("\n");
}
void mwrite (int sock, char * buf, int size)
{
int n = send( sock, buf, size, 0 );
if (n < 0)
{
perror("ERROR writing to socket");
return;
}
printf("Bytes Sent: %d\n", n);
}
int main(int argc, char *argv[])
{
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[256];
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
return(0);
}
portno = atoi(argv[2]);
/* Create a socket point */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
{
perror("ERROR opening socket");
return(1);
}
server = gethostbyname(argv[1]);
if (server == NULL)
{fprintf(stderr,"ERROR no such host \n");
exit(0);}
//printf("host %s, port %d\n", host.c_str(), portno);
bzero((char *) &serv_addr , sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr, (char*)&serv_addr.sin_addr.s_addr, server->h_length);
//serv_addr.sin_addr.s_addr = inet_addr( host.c_str() ); // ( "127.0.0.1" );
serv_addr.sin_port = htons( portno );
/* Now connect to the server */
if (connect( sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr) ) < 0)
{
perror("ERROR connecting");
return(1);
}
printf("Please enter the message=");
bzero(buffer,256);
fgets(buffer,255,stdin);
n= write(sockfd,buffer,strlen(buffer));
if(n<0)
printf("ERROR writing in socket %d len %d", n, strlen(buffer));
bzero(buffer,256);
n = read(sockfd, buffer, 255);
if(n<0)
perror("ERROR reading from socket");
printf("%s\n",buffer);
close(sockfd);
return 0;
buffer[0] = 0x0d;
buffer[1] = 0x0a;
mwrite ( sockfd, buffer, 2);
printf("read 1 ");
read(sockfd);
mwrite( sockfd, buf1, sizeof(buf1));
sleep(2);
mwrite( sockfd, buf2, sizeof(buf2));
printf("read 2 ");
read(sockfd);
mwrite( sockfd, buf3, sizeof(buf3));
printf("read 3a ");
read(sockfd);
sleep(2);
mwrite( sockfd, buf4, sizeof(buf4));
printf("read 3b ");
read(sockfd);
mwrite( sockfd, buf5, sizeof(buf5));
sleep(2);
mwrite( sockfd, buf6, sizeof(buf6));
printf("read 4 ");
read(sockfd);
mwrite( sockfd, buf7, sizeof(buf7));
sleep(2);
mwrite( sockfd, buf8, sizeof(buf8));
read(sockfd);
mwrite ( sockfd, buffer, 2);
read(sockfd);
return 0;
}
Server.cpp
enter code here :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
void error(char *msg)
{
perror(msg);
exit(1);
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno;
//unsigned clilen;
socklen_t clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
if (argc < 2)
{
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
{
error("ERROR opening socket");
}
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
{
error("ERROR on binding");
}
listen(sockfd,5);
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
{
error("ERROR on accept");
}
bzero(buffer,256);
n = read(newsockfd,buffer,255);
if (n < 0)
{
error("ERROR reading from socket");
}
printf("Here is the message: %s\n",buffer);
n = write(newsockfd,"I got your message",18);
if (n < 0)
{
error("ERROR writing to socket");
}
return 0;
}
提前致谢。
最佳答案
[评论开始太多了，所以我写了一个答案。]
至于您的问题，它实际上不是一个单一的问题，而是两个相互交织的问题:缓冲和协商。您需要缓冲，因为TCP是流协议(protocol)，接收调用可能只接收一部分telnet消息，而发送调用可能只发送一部分telnet消息。第二个问题是协商，为此您需要一个所谓的状态机。每个选项需要一个状态。
您还需要阅读和理解RFC854和RFC855。有关RFC的完整列表，请参见Telnet Wikipedia article。
对于选项协商，WILL或WONT响应DO和DONT。除非您已经收到DO或DONT，否则通常不应该发送WILL或WONT。对于初学者，在您正确实现选项之前，我建议您始终在收到DONT(或当然是WILL)消息时始终使用WONT回答。除非您确实需要就某个选项进行协商，否则请不要发送WILL或WONT。
从实现的角度来看，我建议使用四个状态表，每个状态表分别用于发送的WILL，WONT，DO和DONT。这些表包含简单的 bool 值，它们告诉您是否已将相应的消息发送给对等方。这四个表假定您收到的任何无法识别的选项都使用DONT或WONT进行了回复。
如果发送WILL，则在相应的状态表中对其进行标记，这样，当您收到该选项的DO或DONT时，您就知道是发起了协商。
关于c++ - 带有协商的Telnet客户端服务器 session ，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/25999257/