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我试图通过套接字发送一个修改后的字符串。目标是从客户端获取一个字符串，添加一些内容，然后发回。这些字符串通过命令行参数传递。现在，我可以收到消息从客户端，但由于某些原因，我recvfrom函数返回-1这会导致客户先挂了，而不是从服务器接收sendto。看起来服务器正在修改字符串，但我无法在另一侧正确接收它。我的代码中有用于测试目的的打印语句。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。下面是我的代码：Ç - 发送修改后的字符串通过套接字
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);
}
'的strcat（缓冲液，““）;'缓冲器** **不空终止。你有'len = recvfrom（...）'::使用它。 – wildplasser
'len'评估为-1，因为'recvfrom'正在返回。我无法使用它。 'recvfrom'函数有问题。 –
当系统调用返回'-1'时，表示出现错误，'errno'包含错误代码。调用'perror（）'来打印原因。 – Barmar