数据可以在两台使用 C 语言实现 Socket 编程的计算机之间传输。
在同样的情况下，可以轻松地通过实现用户数据报协议 (UDP) 和 简单的客户端/服务器。
安全性 - 通过加密处理。
协议 - UDP
加密 - 异或加密
算法
服务器启动并等待文件名。
-
客户端发送文件名。
该文件名由服务器接收。如果文件存在，服务器开始读取文件，并继续发送一个填充有加密文件内容的缓冲区，直到到达文件末尾。
文件结尾标记为EOF。
文件将作为缓冲区接收，直到且除非收到 EOF。之后对其进行加密。
如果文件不存在，则会发送一条消息“找不到文件”。
服务器
// server code for UDP socket programming #include#include #include #include #include #include #include #include #define IP_Protocol 0 #define Port_No 15050 #define Net_Buf_Size 32 #define CipherKey 'S' #define SendRecvFlag 0 #define NoFile "File Not Found!" // function for clearing buffer void clearBuf(char* b1){ int i; for (i = 0; i < Net_Buf_Size; i++) b1[i] = '\0'; } // function for encryption method char Cipher(char ch1){ return ch1 ^ CipherKey; } // function for sending file int sendFile(FILE* fp1, char* buf1, int s1){ int i, len; if (fp1 == NULL) { strcpy(buf1, NoFile); len = strlen(NoFile); buf1[len] = EOF; for (i = 0; i <= len; i++) buf1[i] = Cipher(buf1[i]); return 1; } char ch1, ch2; for (i = 0; i < s1; i++) { ch1= fgetc(fp); ch2 = Cipher(ch1); buf1[i] = ch2; if (ch1 == EOF) return 1; } return 0; } // driver code int main(){ int sockfd1, nBytes; struct sockaddr_in addr_con; int addrlen = sizeof(addr_con); addr_con.sin_family = AF_INET; addr_con.sin_port = htons(Port_No); addr_con.sin_addr.s_addr = INADDR_ANY; char net_buf1[Net_Buf_Size]; FILE* fp1; // socket() sockfd1 = socket(AF_INET, SOCK_DGRAM, IP_Protocol); if (sockfd1 < 0) printf(" file descriptor is not received!!
"); else printf("
file descriptor %d is received
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", sockfd1); // bind() if (bind(sockfd1, (struct sockaddr*)&addr_con, sizeof(addr_con)) == 0) printf("
Successfully is binded!
"); else printf("
Binding is Failed!
"); while (1) { printf("
Waiting for name of file...
"); // receive name of file clearBuf(net_buf1); nBytes = recvfrom(sockfd1, net_buf1, Net_Buf_Size, SendRecvFlag, (struct sockaddr*)&addr_con, &addrlen); fp1 = fopen(net_buf1, "r"); printf("
File Name is Received: %s
", net_buf1); if (fp1 == NULL) printf("
File open is failed!
"); else printf("
File Successfully is opened!
"); while (1) { // process if (sendFile(fp1, net_buf1, Net_Buf_Size)) { sendto(sockfd1, net_buf1, Net_Buf_Size, SendRecvFlag, (struct sockaddr*)&addr_con, addrlen); break; } // send sendto(sockfd1, net_buf1, Net_Buf_Size, SendRecvFlag, (struct sockaddr*)&addr_con, addrlen); clearBuf(net_buf1); } if (fp1 != NULL) fclose(fp1); } return 0; }
客户端
// client code for UDP socket programming #include#include #include #include #include #include #include #include #define IP_Protocol 0 #define IP_Address "127.0.0.1" // localhost #define Port_No 15050 #define Net_Buf_Size 32 #define CipherKey 'S' #define SendRecvFlag 0 // function for clearing buffer void clearBuf(char* b1){ int i; for (i = 0; i < Net_Buf_Size; i++) b1[i] = '\0'; } // function for decryption method char Cipher(char ch1){ return ch1 ^ CipherKey; } // function for receiveing file int recvFile(char* buf1, int s1) { int i; char ch1; for (i = 0; i < s1; i++) { ch1 = buf1[i]; ch1 = Cipher(ch1); if (ch1 == EOF) return 1; else printf("%c", ch1); } return 0; } // driver code int main(){ int sockfd1, nBytes; struct sockaddr_in addr_con; int addrlen = sizeof(addr_con); addr_con.sin_family = AF_INET; addr_con.sin_port = htons(Port_No); addr_con.sin_addr.s_addr = inet_addr(IP_Address); char net_buf1[Net_Buf_Size]; FILE* fp1; // socket() sockfd1 = socket(AF_INET, SOCK_DGRAM, IP_Protocol); if (sockfd1 < 0) printf(" file descriptor is not received!!
"); else printf("
file descriptor %d is received
", sockfd1); while (1) { printf("
Please enter the name of file to receive:
"); scanf("%s", net_buf1); sendto(sockfd1, net_buf1, Net_Buf_Size, SendRecvFlag, (struct sockaddr*)&addr_con, addrlen); printf("
---------Data is Received---------
"); while (1) { // receive clearBuf(net_buf1); nBytes = recvfrom(sockfd1, net_buf1, Net_Buf_Size, SendRecvFlag, (struct sockaddr*)&addr_con, &addrlen); // process if (recvFile(net_buf1, Net_Buf_Size)) { break; } } printf("
-------------------------------
"); } return 0; }
