Xcode C++ socket programming parse Issue Expected expression - c++

Question

I'm a newbie to socket programming and I'm trying to write a fork() function to enable the client to receive information sent by each four servers.
This is piece of the code I wrote, but it says parse Issue Expected expression.
I checked everything, used the "show invisible' but didn't work, the problem persist.
int pid = fork();
if(pid == 0)
{
close(tcp_socket);
char buffer[255]={0};
int bytes_num;
char serID[] = "0";
//std::string serID = "0";
// char serID[7] = "0";
while(true)
{
//recv(int sockfd, void *buf, size_t len, int flags);
bytes_num = recv(tcp_socket2,buffer,254,0);
if(bytes_num == 0)
{
break;
}
if(serID[] == "0")---------------->problem here
{
serID[]= buffer[0];
}
printf("serverID %s\n", serID);
if(serID[]=="serverA")---------------->problem here
{
//printf("NOW files!\n");
strcpy(str_file1[msg_num1],buffer);
msg_num1++;
}
if(serID[]=="serverB")---------------->problem here
{
strcpy(str_file2[msg_num2],buffer);
msg_num2++;
}
if(serID[]=="serverC")---------------->problem here
{
strcpy(str_file3[msg_num3],buffer);
msg_num3++;
}
if(serID[]=="serverD")---------------->problem here
{
strcpy(str_file4[msg_num4],buffer);
msg_num4++;
}
memset(buffer,0,sizeof(buffer));
}
if((serID[]=="serverA"))---------------->problem here
{
pf_file1 = fopen("rcvd_fileA.txt","w");
for(int i=0; i< msg_num1;i++)
{
//printf("now we read files!\n");
fprintf(pf_file1,"%s\n",str_file1[i]);
}
fclose(pf_file1);
}
if((serID[]=="serverB"))---------------->problem here
{
pf_file2 = fopen("rcvd_fileB.txt","w");
for(int i=0; i< msg_num2;i++)
{
fprintf(pf_file2,"%s\n",str_file2[i]);
}
fclose(pf_file2);
}
if((serID[]=="serverC"))---------------->problem here
{
pf_file3 = fopen("rcvd_fileC.txt","w");
for(int i=0; i< msg_num3;i++)
{
fprintf(pf_file3,"%s\n",str_file3[i]);
}
fclose(pf_file3);
}
if((serID[]=="serverD"))---------------->problem here
{
pf_file4 = fopen("rcvd_fileD.txt","w");
for(int i=0; i< msg_num4;i++)
{
fprintf(pf_file4,"%s\n",str_file4[i]);
}
fclose(pf_file4);
}
printf("The Client receives neighbor information from the Server %s with TCP port number %d and IP address %s \n",serID.c_str(),ntohs(sin.sin_port), ipstr);
close(tcp_socket2);
// printf("The Server %c has the following neighbor information: \n",serverID);
return 0;
}
////////////////////
I would really appreciate any one could help! Thanks in advance!