我正在尝试通过套接字发送修改后的字符串 . 目标是从客户端获取一个字符串,向其添加内容,然后将其发回 . 字符串在命令行参数中传递 . 现在,我可以从客户端收到消息,但由于某种原因,我的 recvfrom
函数返回 -1
,导致客户端挂起并且没有从服务器接收 sendto
. 看起来服务器正在修改字符串,但我不能让它在另一边正确接收 . 我的代码中有打印语句用于测试目的 . 客户端的命令行参数是服务器名称,端口号,字符串 . 服务器的命令行参数是端口号,要连接的字符串 . 以下是我的代码:
headerFiles.h:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/wait.h>
server.c:
#include "headerFiles.h"
int main(int argc, char* argv[])
{
int s;
int len;
char buffer[256];
struct sockaddr_in servAddr;
struct sockaddr_in clntAddr;
int clntAddrLen;
int serverPort;
char catStringMeow[256];
serverPort = atoi(argv[1]);
strcpy(catStringMeow, argv[2]);
// Build local (server) socket address
memset(&servAddr, 0, sizeof(servAddr));
servAddr.sin_family = AF_INET;
servAddr.sin_port = htons(serverPort);
servAddr.sin_addr.s_addr = htonl(INADDR_ANY);
// Create socket
if((s = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
{
perror("Error: socket failed!");
exit(1);
}
// Bind socket to local address and port
if((bind(s, (struct sockaddr*)&servAddr, sizeof(servAddr)) < 0))
{
perror("Error: bind failed!");
exit(1);
}
for(;;) // Runs forever
{
printf("buffer = %s\n", buffer);
printf("In for\n");
// Receive String
len = recvfrom(s, buffer, sizeof(buffer), 0, (struct sockaddr*)&clntAddr, &clntAddrLen);
printf("Received %d bytes\n", len);
printf("buffer = %s\n", buffer);
strcat(buffer, " ");
strcat(buffer, catStringMeow);
printf("New string = %s\n",buffer);
printf("buffer size = %d\n", (int)strlen(buffer));
len = (int)strlen(buffer);
// Send String
sendto(s, buffer, len, 0, (struct sockaddr*)&clntAddr, sizeof(clntAddr));
printf("Sent %d bytes\n", len);
}
}
client.c:
#include "headerFiles.h"
int main (int argc, char* argv[]) // Three arguments to be checked later
{
int s; // Socket descriptor
int len; // Length of string to be echoed
char* servName; // Server name
int servPort; // Server port
char* string; // String to be echoed
char buffer[256+1]; // Data buffer
struct sockaddr_in servAddr; // Server socket address
// Check and set program arguments
if(argc != 4)
{
printf("Error: three arguments are needed!\n");
exit(1);
}
servName = argv[1];
servPort = atoi(argv[2]);
string = argv[3];
// Build server socket address
memset(&servAddr, 0, sizeof(servAddr));
servAddr.sin_family = AF_INET;
inet_pton(AF_INET, servName, &servAddr.sin_addr);
servAddr.sin_port = htons(servPort);
// Create socket
if((s = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
{
perror("Error: Socket failed!");
exit(1);
}
// Send echo string
len = sendto(s, string, strlen(string), 0, (struct sockaddr*) &servAddr, sizeof(servAddr));
printf("Sent %d bytes\n", len);
// Receive echo string
len = recvfrom(s, buffer, len, 0, NULL, NULL);
printf("Received\n");
//Print and verify echoed string
buffer[len] = '\0';
printf("Echo string received: ");
fputs(buffer, stdout);
printf("\n");
// Close the socket
close(s);
// Stop the program
exit(0);
}
3 回答
做
并使缓冲区更大 .
您将未经启发的
clntAddrLen
值传递给recvfrom
,这会产生Invalid argument
错误代码 . 根据documentation:所以你需要初始化它:
在sendto或recvfrom中使用之前,请确保初始化客户端地址长度变量 .
问题是,在第一次从client.c调用sendto时,服务器将客户端的ip视为0.0.0.0,之后在第二个,第三个,...调用client.c获取一个ip并拥有合法的ip例如127.0.0.3:3212 .
你可以看到第二,第三,......客户工作 .
将length变量初始化为sizeof(struct sockaddr_in)