tftp client not receiving from server (send to wrong port)

Question

I'm writing my own TFTP-client. The client is written in c++ (part wise c) and runs on a unix system (Linux Debian stable).

Here is my problem:

I can send my read-request(RRQ) to the TFTP-server(Open TFTP Server on Windows XP). The TFTP-server receives the RRQ, but can't send the answer.

On the server side I see this message: Client 192.168.1.110:55239 C:\OpenTFTPServer\test.txt, Communication Error

But the port 55239 is not the port I defined in my TFTP-Client.

Here are my code-parts:

• set client and server adresses:

  memset(&servaddr,0,sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(servport); // servport=69
  servaddr.sin_addr.s_addr = inet_addr("192.168.1.152"); 
  
  memset(&cliaddr,0,sizeof(cliaddr));
  cliaddr.sin_family = AF_INET;
  cliaddr.sin_port = htons(cliport); // cliport=13337
  cliaddr.sin_addr.s_addr = inet_addr("192.168.1.110");
  

• connect & bind:

  if (connect(serv, (struct sockaddr *) &servaddr, serv_length) < 0)
  {
      bail("Unable to connect with the server!");
  }
  if(bind(cli, (struct sockaddr *)&cliaddr, cli_length)<0)
  {
      bail("Unable to bind to adr & port!");
  }
  

• create TFTP request:

  memset( &cBuf1, 0, sizeof cBuf1);
  rdwrFrame = (struct tftp_wr_rq *)&cBuf1;
  rdwrFrame->opcode=htons(1);
  rdwrFrame->data={'t','e','s','t','.','t','x','t','\0','o','c','t','e','t','\0'};
  

• send TFTP request:

  if (sendto (serv,cBuf1,19,0,(struct sockaddr *)&servaddr,serv_length) < 0)
  {
      bail ("Send the first requirment Frame error -- UDP");
  }
  

Here is my question:

What am I doing wrong, that the TFTP-Server receives the wrong port? I thought it should be set with cliaddr.sin_port = htons(cliport);

Thanks for your help & regards Rico

Answer:

My problem was, that I combined the wrong sockets with the wrong address structs

Here are my working code-parts:

• create sockets:

  serv = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if (serv < 0)
  {
      bail("Unable to create socket tx!");
  }
  
  cli = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if (cli < 0)
  {
      bail("Unable to create socket rx!");
  }
  

• set client and server adresses:

  memset(&servaddr,0,sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(servport);
  servaddr.sin_addr.s_addr = inet_addr("192.168.1.152"); 
  
  memset(&cliaddr,0,sizeof(cliaddr));
  cliaddr.sin_family = AF_INET;
  cliaddr.sin_port = htons(cliport);
  cliaddr.sin_addr.s_addr = inet_addr("192.168.1.110");
  

• connect & bind:

  if(bind(cli, (struct sockaddr *)&cliaddr, cli_length)<0)
  {
      bail("Unable to bind to adr & port!");
  }
  
  if (connect(serv, (struct sockaddr *) &servaddr, serv_length) < 0)
  {
      bail("Unable to connect with the server!");
  }
  

• create TFTP-Request:

  memset( &cBuf1, 0, sizeof cBuf1);
  rdwrFrame = (struct tftp_wr_rq *)&cBuf1;
  rdwrFrame->opcode=htons(1);
  rdwrFrame->data={'t','e','s','t','.','t','x','t',(char)0,'o','c','t','e','t',(char)0};
  

• send TFTP-Request:

  if (sendto (cli,cBuf1,19,0,(struct sockaddr *)&servaddr,serv_length) < 0)
  {
      bail ("Send the first requirment Frame error -- UDP");
  }
  

• receive Data:

  recvfrom(cli,cBuf2,19,0,(struct sockaddr *)&cliaddr,(socklen_t*)&cli_length);
  

Answer 1

I added the answer separatly, so nobody has to search it in the original post.

Answer:

My problem was, that I combined the wrong sockets with the wrong address structs

Here are my working code-parts:

• create sockets:

  serv = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if (serv < 0)
  {
      bail("Unable to create socket tx!");
  }
  
  cli = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if (cli < 0)
  {
      bail("Unable to create socket rx!");
  }
  

• set client and server adresses:

  memset(&servaddr,0,sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(servport);
  servaddr.sin_addr.s_addr = inet_addr("192.168.1.152"); 
  
  memset(&cliaddr,0,sizeof(cliaddr));
  cliaddr.sin_family = AF_INET;
  cliaddr.sin_port = htons(cliport);
  cliaddr.sin_addr.s_addr = inet_addr("192.168.1.110");
  

• connect & bind:

  if(bind(cli, (struct sockaddr *)&cliaddr, cli_length)<0)
  {
      bail("Unable to bind to adr & port!");
  }
  
  if (connect(serv, (struct sockaddr *) &servaddr, serv_length) < 0)
  {
      bail("Unable to connect with the server!");
  }
  

• create TFTP-Request:

  memset( &cBuf1, 0, sizeof cBuf1);
  rdwrFrame = (struct tftp_wr_rq *)&cBuf1;
  rdwrFrame->opcode=htons(1);
  rdwrFrame->data={'t','e','s','t','.','t','x','t',(char)0,'o','c','t','e','t',(char)0};
  

• send TFTP-Request:

  if (sendto (cli,cBuf1,19,0,(struct sockaddr *)&servaddr,serv_length) < 0)
  {
      bail ("Send the first requirment Frame error -- UDP");
  }
  

• receive Data:

  recvfrom(cli,cBuf2,19,0,(struct sockaddr *)&cliaddr,(socklen_t*)&cli_length);