与谈判的Telnet客户端服务器会话
我正在尝试为它们之间发送协商的Telnet客户端服务器会话编写代码。像Will一样,不会,不会。我使用socket编程编写了一个基本的客户端服务器程序。 如果我能知道如何通过协商将客户端/服务器修改为telnet客户端服务器,那将会非常有帮助。以下是代码:与谈判的Telnet客户端服务器会话
提前这里
#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;
}
输入代码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;
}
感谢。
[它开始是太多意见,所以我写一个答案,而不是]
至于你的问题,它实际上不是一个单一的问题,而是两个混杂问题:缓冲和谈判。您需要缓冲,因为TCP是一种流媒体协议,接收呼叫可能只接收telnet消息的一部分,而发送呼叫可能只发送一部分telnet消息。第二个问题是谈判,为此你需要一个所谓的状态机。每个选项你需要一个状态。
您还需要阅读并理解RFC854和RFC855。请参阅Telnet Wikipedia article以获取RFC的完整列表。
对于期权协商,WILL
和WONT
由DO
或DONT
作出响应。除非您已收到WILL
或WONT
,否则通常不应发送DO
或DONT
。对于初学者来说,除非您正确处理选项,否则无论何时获得WILL
(或课程WONT
)消息,我都建议您始终以DONT
回答。除非您确实需要谈判某个选项,否则请勿发送WILL
或WONT
。
更多实现的角度来看,我建议四个态表,每一个WILL
,WONT
,DO
和DONT
是你就差了。这些表格包含简单的布尔值,告诉您是否已将相应的消息发送给对等体。这四张表格假设您收到的任何未识别的选项都会以DONT
或WONT
回答。
如果您发送WILL
,则将其标记在相应的状态表中,以便在收到DO
或DONT
的选项时,您知道是您启动了协商。
它不一定需要用状态机来实现。其他健壮且合规的实施方法是可能的。然而,状态机可以说是最清晰的,并且在稳健性方面可能是最简单的方法,所以推荐使用+1。 – blubberdiblub 2017-01-03 09:28:27
我建议不要在缓冲区中使用“幻数”。 ''arpa/telnet.h>'头文件包含你需要的所有常量。使用它们会使这些缓冲区至少更具可读性。 – 2014-09-23 15:43:43