android - 从 Android 接收 C 语言服务器上的字节

Question

我已成功将我的 Android 手机作为客户端连接到作为服务器的树莓派。

下一步是使用字节向树莓派发送数据。我在 Java 中为 Android 做的正确吗？

socket.getOutputStream().write(String.valueOf(progress).getBytes());

此后，在我的树莓派端，我将不得不接收 C 中的字节。我在服务器上接收数据时遇到问题。这是我的代码。

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>

int main(){
  int welcomeSocket,clientSocket;
  char buffer[1024];
  struct sockaddr_in serverAddr;
  struct sockaddr_storage serverStorage;
  socklen_t addr_size;
  ssize_t nread;

  /*---- Create the socket. The three arguments are: ----*/
  /* 1) Internet domain 2) Stream socket 3) Default protocol (TCP in this case) */
  welcomeSocket = socket(PF_INET, SOCK_STREAM, 0);

  /*---- Configure settings of the server address struct ----*/
  /* Address family = Internet */
  serverAddr.sin_family = AF_INET;
  /* Set port number, using htons function to use proper byte order */
  serverAddr.sin_port = htons(9999);
  /* Set IP address to localhost */
  serverAddr.sin_addr.s_addr = INADDR_ANY;
  /* Set all bits of the padding field to 0 */
  memset(serverAddr.sin_zero, '\0', sizeof serverAddr.sin_zero);  

  /*---- Bind the address struct to the socket ----*/
  bind(welcomeSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr));

  /*---- Listen on the socket, with 5 max connection requests queued ----*/
  if(listen(welcomeSocket,5)==0){
    printf("Listening\n");
}
  else
    printf("Error\n");

  /*---- Accept call creates a new socket for the incoming connection ----*/
  addr_size = sizeof serverStorage;
  clientSocket = accept(welcomeSocket, (struct sockaddr *) &serverStorage, &addr_size);
  printf("Successfully Connected!!!\n\r");

  //Receive data from android  
  //recv(welcomeSocket,buffer,1024,0);
  nread = recvfrom(clientSocket, buffer,1024, 0, (struct sockaddr *) &serverStorage, &addr_size);
  if(nread==-1)
  perror("Error!");
  else
  printf("Data received: %s",buffer);


return 0;

}

根据Pravin的评论，我尝试使用Recvfrom和perror，它显示错误为-1。

Answer 1

好的!我意识到了问题所在。我意识到我没有使用之前创建的客户端套接字。我继续使用服务器的套接字哈哈。一开始没注意到。我用一个例子来看看我的服务器和示例服务器之间有什么不同，这真的很有帮助!

http://www.binarytides.com/server-client-example-c-sockets-linux/