我是编程新手;我需要将一些浮点值从 C++ 程序发送到另一个 C 程序。我在互联网上找到了这个示例代码并设法使其正常工作:
服务器:
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
#define LISTENQ 8 /*maximum number of client connections */
int main (int argc, char **argv)
{
int listenfd, connfd, n;
socklen_t clilen;
char buf[MAXLINE];
struct sockaddr_in cliaddr, servaddr;
//creation of the socket
listenfd = socket (AF_INET, SOCK_STREAM, 0);
//preparation of the socket address
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
listen(listenfd, LISTENQ);
printf("%s\n","Server running...waiting for connections.");
for ( ; ; ) {
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen);
printf("%s\n","Received request...");
while ( (n = recv(connfd, buf, MAXLINE,0)) > 0) {
printf("%s","String received from and resent to the client:");
puts(buf);
send(connfd, buf, n, 0);
}
if (n < 0) {
perror("Read error");
exit(1);
}
close(connfd);
}
//close listening socket
close(listenfd);
}
客户:
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
int
main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
char sendline[MAXLINE], recvline[MAXLINE];
//basic check of the arguments
//additional checks can be inserted
if (argc !=2) {
perror("Usage: TCPClient <IP address of the server");
exit(1);
}
//Create a socket for the client
//If sockfd<0 there was an error in the creation of the socket
if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) <0) {
perror("Problem in creating the socket");
exit(2);
}
//Creation of the socket
memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr= inet_addr(argv[1]);
servaddr.sin_port = htons(SERV_PORT); //convert to big-endian order
//Connection of the client to the socket
if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr))<0) {
perror("Problem in connecting to the server");
exit(3);
}
while (fgets(sendline, MAXLINE, stdin) != NULL) {
send(sockfd, sendline, strlen(sendline), 0);
if (recv(sockfd, recvline, MAXLINE,0) == 0){
//error: server terminated prematurely
perror("The server terminated prematurely");
exit(4);
}
printf("%s", "String received from the server: ");
fputs(recvline, stdout);
}
exit(0);
}
那么我必须添加什么才能将浮点值发送到服务器并将其取回?这些机器都是基于 x86 的,一台安装了 Debian 6,另一台安装了 Linux Mint。我尝试了两种方式(带客户端的 Debian 和带服务器的 Linux Mint 以及带服务器的 Debian 和带客户端的 Linux Mint)并且它工作正常。
我 m thinking about making some casting between a char value and float... It
那可能吗?有什么办法可以不用转换就可以发送吗?我不需要 char 值,只需要一些 float 值。
感谢您的帮助!
编辑:我尝试使用 snprintf 和 sscanf,但我做错了,因为它不能正常工作。这是目前的客户端和服务器:
客户:
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
int
main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
char sendline[MAXLINE], recvline[MAXLINE], buffer [256];
//Añadidas por mi//
float a, b, c;
a = 0;
b = 0;
c = 0;
c = a + b;
printf("\nPrimer numero: ");
scanf("%f", &a);
printf ("\nSegundo numero: ");
scanf ("%f", &b);
sprintf(buffer, "%f", sizeof c, c);
unsigned char len = strlen(buffer);
//basic check of the arguments
//additional checks can be inserted
if (argc !=2) {
perror("Usage: TCPClient <IP address of the server");
exit(1);
}
//Create a socket for the client
//If sockfd<0 there was an error in the creation of the socket
if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) <0) {
perror("Problem in creating the socket");
exit(2);
}
//Creation of the socket
memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr= inet_addr(argv[1]);
servaddr.sin_port = htons(SERV_PORT); //convert to big-endian order
//Connection of the client to the socket
if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr))<0) {
perror("Problem in connecting to the server");
exit(3);
}
while (fgets(sendline, MAXLINE, stdin) != NULL) {
send(sockfd, sendline, strlen(sendline), 0);
send(sockfd, &len, sizeof len, 0);
send (sockfd, buffer, sizeof buffer, 0);
if (recv(sockfd, recvline, MAXLINE,0) == 0){
//error: server terminated prematurely
perror("The server terminated prematurely");
exit(4);
}
printf("%s", "String received from the server: ");
fputs(recvline, stdout);
}
exit(0);
}
服务器:
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
#define LISTENQ 8 /*maximum number of client connections */
int main (int argc, char **argv)
{
float c;
int listenfd, connfd, n;
socklen_t clilen;
char buf[MAXLINE], buf256[256], buffer[256];
unsigned char len = strlen(buffer);
struct sockaddr_in cliaddr, servaddr;
//creation of the socket
listenfd = socket (AF_INET, SOCK_STREAM, 0);
//preparation of the socket address
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
listen(listenfd, LISTENQ);
printf("%s\n","Server running...waiting for connections.");
for ( ; ; ) {
clilen = sizeof(cliaddr);
connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen);
printf("%s\n","Received request...");
while ( (n = recv(connfd, buf, MAXLINE,0)) > 0) {
printf("%s","String received from and resent to the client:");
puts(buf);
recv(connfd, &len, sizeof len, 0);
recv(connfd, buf256, len, 0);
recv(connfd, buffer, 256, 0);
buf256[len] = 0;
sscanf(buffer, "%f", &c);
puts(buffer);
printf ("\n%f", &c);
send(connfd, buf, n, 0);
}
if (n < 0) {
perror("Read error");
exit(1);
}
close(connfd);
}
//close listening socket
close(listenfd);
}
这些程序工作起来很奇怪,它显示像 0.0000e 这样的值,有时什么都不显示。我需要发送各种浮点值,所以这个程序只是一个关于如何发送一个浮点值的例子。任何人都可以看到我的程序中的错误在哪里吗?谢谢!
最佳答案
代码可以使用二进制表示形式发送float
。这可能适用于匹配良好的系统,否则可能会由于不同的 float
表示或字节顺序而失败。 @clarasoft-it
float x = ...;
// send
send(sockfd, &x, sizeof x, 0);
// receive
recv(connfd, &x, sizeof x, 0);
替代代码可以发送 float
使用字符串表示打印 sufficient digits .这个更便携。它没有字节序问题。它确实需要传送字符串长度信息。 @user3386109 @EOF
如果末尾的浮点格式不同,范围和精度问题可能需要额外处理,无论使用何种方法,这都是一个问题。
#include <float.h>
#define FLT_EXPO_SIZE 5
// send
// create a buffer large enough
// - d . ddddd e - expo \0
char buf[1 + 1 + 1 + (FLT_DECIMAL_DIG - 1) + 1 + 1 + FLT_EXPO_SIZE + 1];
// print the value to enough digits to distinguish x from all other float
unsigned char len = sprintf(buf, "%.*e", FLT_DECIMAL_DIG - 1, x);
send(sockfd, &len, sizeof len, 0);
send(sockfd, buf, sizeof buf, 0);
// receive
char buf256[256];
recv(connfd, &len, sizeof len, 0);
recv(connfd, buf256, len, 0);
buf256[len] = 0;
sscanf(buf256, "%f", &x); // add sscanf() check
注意事项:
与保守的 5 相比,可以使用其他代码更好地定义
FLT_EXPO_SIZE
。基于FLT_MIN_EXP
、FLT_MAX_EXP
和可能FLT_TRUE_MIN
。可以使用
sprintf("%a", x);
进行十六进制表示。在这种情况下需要 TBD 缓冲区大小。仍然可以使用sscanf(buf, "%f", &x)
可以使用
snprintf()
。为简洁起见省略了各种错误检查。
关于c++ - 在套接字 C/C++ 上发送浮点值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38511305/