如何從服務器發送查詢和使用Telnet庫

Question

，其中客戶端發送存儲在緩衝區字符到服務器的Telnet談判我寫了一個套接字程序從客戶端接收的回聲。服務器接收它，並與每個buffer.Here的消息長度響應是代碼：

Server.cpp

#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 <arpa/telnet.h> 
#include <unistd.h> 


void error(char *msg) 
{ 
perror(msg); 
exit(1); 
} 

int main(int argc, char *argv[]) 
{ 

int sockfd, newsockfd, portno; 
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) 
{ 
perror("ERROR opening socket"); 
exit(1); 
} 

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) 
{ 
perror("ERROR on binding"); 
exit(1); 
} 

    if(listen(sockfd,5)<0) 
    { 
     perror("Error on listen"); 
    } 
     while(1) 
     { 
    clilen = sizeof(cli_addr); 
    newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr, &clilen); 

    if (newsockfd < 0) 
    { 
    perror("ERROR on accept"); 
    exit(1); 
    } 

    //fork to hande this client 
     if (fork() == 0) 
     { // client code no longer need this; 
     close(sockfd); 
      // loop until a closed or error state happens 
     ssize_t n =0; 
     while ((n = read(newsockfd,buffer,sizeof(buffer)-1))>0) 
     { 
      printf("Recieved : %*s\n",static_cast<int>(n),buffer); 

      //send response 
      static const char resp[] = "I got yout message \n"; 

      n = write(newsockfd, resp , sizeof(resp)-1); 
      if(n<0) 
      { 
      perror("Error writing to socket "); 
      exit(1); 
      } 
      } 
     close(newsockfd); 
     exit(0); 
    } 
    close(newsockfd); } 
return 0; 
} 

Client.cpp

#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> 
#include <arpa/telnet.h> 


char buf1[] = {0xff, 0xfb, 0x18, 0xff, 0xfb, 0x1f};     


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("\n%d bytes received buffer is: %s", n, buffer); 
    for (int i = 0; i < n; i++) 
     printf("%2x ", buffer[i]);//printing ascii characters 
    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);} 




    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_port = htons(portno); 

    /* Now connect to the server */ 
    if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) 
    { 
     perror("ERROR connecting"); 
     return(1); 
    } 



n= write(sockfd,buffer,strlen(buffer)); 
    if(n<0) 
    printf("ERROR writing in socket %d len %d", n, strlen(buffer)); 


n = read(sockfd, buffer, 255); 
    if(n<0) 
    perror("ERROR reading from socket"); 

printf("%s\n",buffer); 





    bzero(buffer,256); 
    buffer[0] = 0x0d; 
    buffer[1] = 0x0a; 

    printf("\nSend buff...."); 
    mwrite (sockfd, buffer,2); 
    read(sockfd); 

    mwrite(sockfd, buf1, sizeof(buf1)); 
    printf("\nSend buff1...."); 
    read(sockfd); 


    printf("\nRecieved all negotiation buffers"); 

    close(sockfd); // close socket 

    return 0; 

輸出是： 客戶端輸出：

debian:~/echoserver$ ./client 127.0.0.1 8088 
I got your message 

Send buff....Bytes Sent: 2 

20 bytes received buffer is: I got yout message 
49 20 67 6f 74 20 79 6f 75 74 20 6d 65 73 73 61 67 65 20 a 

Send buf1....Bytes Sent: 6 

20 bytes received buffer is: I got yout message 
49 20 67 6f 74 20 79 6f 75 74 20 6d 65 73 73 61 67 65 20 a 
Recieved all negotiation buffers 

服務器輸出：

@debian:~/echoserver$ ./server 8088 
Recieved : .N=�� 
Recieved : 
=�� 

我也想知道我們是否想要顛倒這個過程，也就是從服務器發送一個3字節的查詢序列到客戶端，其中byte1-解釋爲命令（0xff），byte2-命令碼，byte3 - 選項代碼。 Telnet流式傳輸，因此收到的消息可能包含一個或多個查詢。例如，服務器在接受連接時發送一個3字節的消息（ff，fd，18）。客戶應該只是附和回來不會（FF，FC，18）

如：提前

Server : Sending Query 1 : 0xff,0xfd,0x18 
Client echo : 0xff , 0xfc , 0x18 

感謝。

Answer 1

您的buf數組不是字符串（沒有終止'\0'字符），但您可以撥打strlen()。這會給你不確定的行爲。由於它們是二進制數組，因此改爲使用sizeof。

這在您自己的跟蹤printf() s中清晰可見，第一行顯示「Bytes Sent: 18」，但顯然buf1只有6個字節。

Answer 2

在client.cpp，buffer其首次使用前未初始化。

int main(int argc, char *argv[]) { 
    char buffer[256]; 
    ... 
    n= write(sockfd,buffer,strlen(buffer)); 

當接收到來自一個插座一個「串」，eithe追加一個試運行'\0'或確保發送者發送的HASE它。

n = write(sockfd,buffer,strlen(buffer)+1); 
... 
n = read(sockfd, buffer, sizeof buf - 1); 
if (n > 0 && buffer[n-1] != '\0') { 
    buffer[n-1] = '\0'; 
    n++; 
} 

---

函數簽名不client.cpp排隊，所以即使這被標記C，這是一個C++崗位。

void read (int sock) { ... } 

int main(int argc, char *argv[]) { 
    ... 
    n = read(sockfd, buffer, 255);